Announcer from nbc news World Headquarters in new york this is nbc nightly news with lester holt. Good evening. Well get to the impact of that big selloff on wall street in a moment. But right now weve got late details coming in from france where two americans are injured and are being called heroes in a shooting attack aboard a highspeed train from amsterdam to paris. Without the intervention of the americans were told casualties could have been far worse. French Officials Say a man opened fire with an automatic weapon in whats being called a possible terrorist otack. Nbcs keir simmons is on the story. Reporter the attack left three passengers injured including two americans. At least one of them a member of the u. S. Military. A womans bag is left splattered with blood after a gibman reportedly opened fire aboard a highspeed train from amount ststerdam to paris. The French Interior minister at the scene say the two americans intervened to stop the attacker who was reportedly armed with a kalashnikov rifle, an automatic pistol, and a knife. Without their intervention, he said, we could have faced a terrible tragedy. Cell phone video shows an unidentified man carried across the platform. Witnesses describe the terror on board the train. Translator i asked what happened. He told me we had to stop because theres a man who had a kalashnikov in first class. Reporter another passenger told nbc news, i saw the man who was shot in the neck stumble. He dropped his duffel bag right in the seat across from me and he collapsed on the floor. Antiterrorist officials are leading the investigation into what happened. Ammunition piled up on the platform. Forensic experts on the scene looked for evidence. And tonight a suspect has been arrested. French media say he is a 26yearold moroccan. Once again france in the headlines. Reporter eight months ago terrorist gunmen opened fire at the paris office of Charlie Hebdo magazine, killing 12 people. Today the french president expressed his solidarity to those injured and their loved ones in what could have been a deadly assault, stopped by the quick action of what the french are calling courageous americans. Keir simmons, nbc news, london. There is also late word of a deadly shooting at a Federal Building here in new york during the evening rush. A federal Law Enforcement official says a gunman walked insulate this afternoon and opened fire, hitting a private Security Guard before turning the gun on himself. The motive is unclear. The building houses a federal Detention Center and Immigration Court among other things. Now to todays drama on wall street. If your pension or your 401 k is invested in the stock market, its a good bet you lost money today. In fact, youve probably been losing it for days. An already lousy week on wall street ended today with a huge selloff. The Dow Jones Industrial average plummeting 530 points, or 3 . Thats a 1,000 point loss for the week. And it happened against the backdrop of what indications show to be an improving u. S. Economy. Helping us make sense of it and what it could mean to your bottom line, heres nbcs tom costello. Reporter on wall street today a rout, capping off a month of pain with americans pensions and 401 k s in a sea of red. The Dow Jones Industrial average having its worst day in four years today, dropping 528 points. This is the worst week for the dow since 2011. Reporter the dow, s p, and nasdaq all in a nose dive. The dow has now slid 10 from its alltime high. The biggest reason for the selloff is a world away from americas main streets. The chinese economy is slowing fast, and we live in an interconnected global economy. How bad is china . Its worse than you think. Whatever you might think, its worse. Reporter last week china devalued its currency to make its exports cheaper, sparking concerns of a currency war with the u. S. We dont know whether or not they have the capability to contain their own problems. Theres been a lot of overinvestment there. Theres been a lot of bad investment. Theres been a lot of corruption in the investment thats been made there. We dont quite understand how it all plays out. Reporter also weighing on the markets, the dramatic slide in oil prices, now at a sixyear low, below 40 a barrel. Good news at the pump, where prices are expected to drop to 2 a gallon by the end of the year. Already 2. 19 at this station in dallas. The cheaper the better. Reporter but its bad news for big oil companies, many of which are now laying off employees. Big oip Company Stocks have been hit especially hard on wall street. So what should americans with money in the stock market do now . Experts say it may be best to wait it out. You dont want to panic. Panic is not an investing strategy. You also dont you shouldnt feel compelled to make a decision about investing at a moment in time. In other words, what do i do right now. Reporter the situation in china and the stock market selloff may convince the fed not to raise Interest Rates as expected next month. In fact, some experts think they may now be on hold through the end of the year. Lester . Tom, thanks very much. Lets bring in cnbcs sue he rera. All those things tom ticked off, the chinese economy, oil price, those are going to be in effect monday as they were today. Are we looking at a short flash here or a sustained longerterm slump . I think it is probably, lester, going to be longerterm because our market is watching the chinese officials so closely. Were kind of dependent on how they decide to manage their own economy and their own market. Also, august is traditionally a very volatile month and it certainly is proving that out to be true. So the analysts that im talking to say at least the next few weeks expect more volatility and probably more down side activity in the market and then were going to be going into the fall, which also traditionally has some risk in it as well. You have to really figure out what your risk tolerance is, if youre going to be in the stock market, lester. Sue herea tonight. Thank you. Tonight the president has declared a federal emergency in Washington State. A major disaster as wildfires continue to explode. Growing again overnight. Threatening homes. The situation is getting so desperate officials there are now asking for volunteers to help in the fight. Nearly 100 fires now burning in the west. Our National CorrespondentMiguel Almaguer reports from the front lines. Reporter in parts of Washington State devastation. More evacuations. More homes lost every day. Its all burning now. And we dont have the resources available. Reporter with smoke billowing into the sky, unhealthy air alerts issued in several states, whipping winds are fueling fastmoving fires, burning more than 100 square miles in just over one day. The wind is going every direction. Like a tornado. Kicking up really fast. Reporter in the burn zone firefighters struggle to stay ahead of the flames. Pilots have been making drops here all day long, but the conditions are now blinding. It is really affecting the firefight here. Last night they paused for a procession. A tribute for the three firefighters killed this week. We now know the fire made a 180 degree shift. A vehicle dropping off an embankment, tumbling downhill. Richard wheeler, a tenyear veteran on the fire lines, leaves behind his wife. Andrew zajac was married to a fellow firefighter. His grandfather says he loved the outdoors. Oh, very proud. He was a he was a good boy. A real good boy. Reporter Tom Zbyszewski was just 20. The only child. The son of a firefighter. He was a special kid. You know. Were really going to miss tom. Reporter tonight they honor the dead by continuing the fight. For the first time in Washington State history theyre asking for volunteers who can operate heavy machinery. Alex thomason spent thousands of dollars to buy a fire truck. Now the fulltime lawyer spends his spare time protecting the community. If we can save one persons home, this is absolutely worth it. So here we are. Reporter crews tell us tonight they are worried about the next six hours. Thats when the red flag warning will end. If there is any good news here, it does promise Better Weather over the weekend. Lester . Miguel almaguer, thank you. Hurricane danny has strengthened to a major category 3 storm in the atlantic. Its packing maximum sustained winds of 115 miles per hour. Still about 900 miles away from the islands in the eastern caribbean. Forecasts show it could weaktone a Tropical Storm by the time it arrives there on monday. But it bears watching. Tonight tens of thousands are expected to turn out for the biggest rally weve seen yet on the campaign trail. So many clamoring to hear donald trump speak in alabama they had to move the event to a football stadium that seats well over 30,000. Nbcs katy tur is in mobile. Reporter august in mobile, alabama, where the mercury relentlessly rises to 90 and the mumdty is enough to make you melt in your shoes. Trump for president. Reporter still the curious lined up for hours to see donald trump. Some traveling hundreds of miles. Others were bused here on eight trumpfunded shuttles from town. The campaign initially booked a small mobile ballroom for tonights rally but this week decided to move it to the lad peoples stadium the site of the annual College Senior bowl. Capacity 40,000. So far 36,000 people have rsvped for tonights event according to the campaign, and if they all show up it will be the biggest event so far this political season season. All fueled by Donald Trumps emotional appeals to conservative anger. Hammering on points like border security, birthright citizenship, and linking immigration to crime. We will work with them. They have to go. Chuck, we either have a country or we dont have a country. Minority voters are not a key electorate in the republican primary process. So for those republicans who fear that Donald Trumps rhetoric is too extreme or too alienating, im not sure its going to hurt him within the primary. Reporter during the lunch rush at mobiles famous wencels oyster house where the walls feature this sort of wry commentary politics, the art of looking for trouble, finding it everywhere, diagnosing it wrongly and applying unsuitable remedies. The Perfect Place to talk about trump. Im looking for somebody to cut government down to size. Government has been attacking the people and the people are tired of it. Reporter while not an early voting state, trump is here for a reason. Its the home town of jess sessions, the republican senator who helped him craft his immigration bill. Alabama also passed the harshest Immigration Law back in 2011 before it was mostly struck down by the courts. Lester . All right, katie, thanks. Much more on all things trump, clinton, and the race for the white house sunday morning on meet the press with chuck todd. Confirmation tonight from the white house that the second in command of isis was killed in a u. S. Airstrike last week. It happened while he was in a car driving near mosul, an isis stronghold in iraq. Theres a desperate scene playing out overseas as hundreds of refugees are rushing the Macedonian Border from greece, clashing violently with police. Yesterday a state of emergency was declared to handle the surge. Our cameras were there when hundreds of refugees came ashore in greece just days ago. Tens of thousands who made the journey in recent weeks, most of them blame isis and the killing in syria. Tensions between north and south korea may be at a breaking point this evening. And u. S. Forces may be caught in the middle. North korea, a Nuclear Power and often prone to saber rattling, says it is mobilizing for war, claiming that south korea is provoking a showdown. Nbcs ian williams has our report from seoul, south korea. Reporter north korea is threatening war over these loudspeakers. South korea recently started using them again to broadcast propaganda across the dmz. A provocation, north korea says. On state television threats of military action unless the speakers are removed. The deadline now just hours away. Kim jong un, the norths unpredictable dictator, today declared what he called a quasistate of war and order his troops to prepare for battle. The Demilitarized Zone where north and south korea face off is the most fortified place on earth. The south backed by 28,000 u. S. Troops. U. S. Forces have been there since the korean war. They take part in frequent military exercises with the south, including one under way now. Another provocation, the north says. The loudspeaker dispute triggered an exchange of artillery fire thursday. The two koreas most serious clash in years. Hundreds of border villages were forced to evacuate to underground shelters. This is one of the shelters. Its a pretty heavy bombproof door. This woman told me she was used to heated rhetoric but the shelling made her nervous. With good reason. North korea has nuclear weapons. The whole korean peninsulas a tinder box. So we want to stabilize things. Thats very much in our interests. Reporter but tonight south korea is saying it will strike back hard at any provocation from the north. Ian williams, nbc news, seoul. A lot more to tell you about here. Still ahead tonight, breaking the habit. How a family of five successfully did what so many people are finding impossible right now. Cutting the sugar. And later, a family of a different kind cooling off on a hot summer day. Theres bears in the pool. We live in a pick and choose world. Choose, choose, choose. But at bedtime . Why settle for this . Enter sleep number. Right now all beds are on sale. Sleepiq technology tells you how well you slept and what adjustments you can make. You like the bed soft. Hes more hardcore. So your sleep goes from good to great to wow only at a sleep number store. The time is now for the biggest sale of the year, where all beds are on sale save 50 on the labor Day Limited Edition bed. Save 50 on the labor Day Limited Edition bed. Know better sleep with sleep number. In study after study, advil is unsurpassed in pain relief. Nothing is proven stronger on aches and pains than advil. Not tylenol. Not aleve. Nothing. Relief doesnt get any better than this. Advil. So youre a Small Business expert from at t . Yeah, give me a problem and ive got the solution. Well, we have 30 years of customer records. 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Weve heard a lot this summer about americans trying to dramatically cut back on sugar, and just how hard it is to do. But tonight youre going to meet the one family of five that did it together. Our National Correspondent kate snow reports on their big challenge. Reporter for deirdre diggins dinner time used to mean a crazy mad rush to get some food in her teenagers. Id be throwing food in my mouth and heading out. I was tired of the food preparation. And i think a lot of moms feel that way. Reporter but after her youngest was diagnosed with diabetes she reached out to nutritionist terry rhodes for help, starting with the pantry. Id just take it out and say have as much as you want. Reporter first tip, get rid of those snack bins. This comes in at 27 grams of sugar. So within this amount theyve now exceeded the daily recommended sugar intake. Reporter the American Heart Association says we should be eating between three and nine teaspoons of added sugar a day but the average american is eating 22. The sugar Association Says the evidence is lacking for these recommendations and that suge their moderation can be part of a balanced diet. For breakfast i would have i would say a handful of jelly beans. It was far more than a handful. Reporter Naeemah Clark didnt just quit sugar. Like a growing number of americans she posted her goals on facebook. Because i have said it out loud and my facebook friends knew and my friends at work were telling other people, like i know that im i can stick to this. And i feel good. Im not grumpy about it. Just look at how that difference in sugar is. Reporter in minnesota terry taught deirdre another tip. Dont let your kids dictate the shopping list. Fewer than three grams of sugar and greater than three grams of fiber is terrys general guideline. It was tough on deirdres kids at first. We all were kind of like what . Ice cream just went away . Yeah. That was tough. That was really i miss that a lot. Reporter we had them document the first few days of the diet. Im tired. Feeling kind of tired. Overtired. I keep saying im tired all the time. Reporter but around day four everyone noticed a change. I feel good. Reporter my energy level was more i felt better all day. Its a work in progress but deirdre is hoping she can make the new habits stick. Kate snow, nbc news, chanhassen, minnesota. Were back in a moment with warnings from the cdc. Moment with warnings from the cdc. What you i found her wandering miles from home. When the phone rang at 5am, i knew it was about mom. I see how hard its been on her at work and i want to help. For the 5 million americans living with alzheimers, and millions more who feel its effects. Lets walk together to make an even bigger impact and end alzheimers for good. Find your walk near you at alz. Org walk. 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An Incoming Freshman at Ball State University in muncie, indiana sinking a halfcourt shot to earn a free ride for the first half of the school year. Believe it or not, the school says its the second time in three years a student hit that shot to win tuition for a semester. And any kid playing in the street knows that when the ball gets away sometimes youve just got to let it go. That wasnt an option in toledo when a storm knocked a giant 250pound red ball loose from an art installation and no gutter was big enough to stop it. It rolled over a car and if bent a street sign before it was chased down. When we come back, some pools are too hot. Some pools are too cold. But this one, just cold. But this one, just right. The possibility of a flare swas almost always on my mind. Thinking about what to avoid, where to go. And how to deal with my uc. To me, that was normal. Until i talked to my doctor. She told me that humira helps people like me get uc under control and keep it under control when certain medications havent worked well enough. Humira can lower your ability to fight infections, including tuberculosis. Serious, sometimes fatal infections and cancers, including lymphoma, have happened; as have blood, liver, and nervous system problems, serious allergic reactions, and new or worsening heart failure. Before treatment, get tested for tb. Tell your doctor if youve been to areas where certain fungal infections are common, and if youve had tb, hepatitis b, are prone to infections, or have flulike symptoms or sores. Dont start humira if you have an infection. Raise your expectations. Ask your gastroenterologist about humira. With humira, control is possible. Fedid you know it may be coming . From being on your feet all day . Dr. Scholls custom fit orthotic inserts are uniquely designed to provide immediate all day relief from lower back pain. Ya know, viagra helps guys with erectile dysfunction get and keep an erection. Talk to your doctor about viagra. Ask your doctor if your heart is healthy enough for sex. Do not take viagra if you take nitrates for chest pain; it may cause an unsafe drop in blood pressure. Side effects include headache, flushing, upset stomach and abnormal vision. To avoid longterm injury, seek immediate medical help for an erection lasting more than four hours. Stop taking viagra and call your doctor right away if you experience a sudden decrease or loss in vision or hearing. Ask your doctor about viagra. We end tonight with what has to be the video of the day or id even say the year. Its a mom taking her kids for a dip in a back yard pool just like any other family, except you probably wouldnt want to play a game of marco polo with them. Heres stephanie gosk. Reporter on a hot summer day when the woods in new jersey can really get unbearable, whats a mother of five supposed to do . Theres bears in the Pool Reporter but the two children who normally get to use the pool arent exactly happy about it. They took my floaty i know, well buy a new one. Reporter and there are some practical concerns about a family of bears in the back yard pool. When the mother gets out, im afraid shes going to collapse the pool. Reporter the video posted by the basso family is irresistible, in part because the bears are so relatable. Two are fighting. Theyre playing. Theyre brothers and sisters. Reporter some roughhousing, some take turns on the slide, going down and up the wrong way. Look at this moment. A cup makes the ageold mistake of pestering mom when all she wants to do is relax. The penalty a roughly enforced pool time out. At some point it just gets to be too much for the bassos. The pool is a mess, the toys are chewed up. Oh, thats not good. Reporter and the pool filter is ripped out. Despite all the fun they are having the police are here. Reporter its time for the bear family to go. Maybe theyre scared of the police. Reporter busted one too many times perhaps. Oh, my goodness. Reporter stephanie gosk, nbc news, new york. Ive got nothing else that can top that. Thats going to do it for us on a friday night. Im lester holt. For all of us at nbc news, thank you for watching. Have a great weekend and good night. Breaking Sofia Vergara wedding news. The invitations gone out and weve got all the details. Now on extra. Sofia vergara and joe finally get married. When is it . Where is it . Are you one of those bridezillas. Couples new scandal. New yorks nba wife lala fighting accusations of cheating. The instagram attack we cant say on television. Miranda lambert postdivorce make over. Caitlyn jenner versus kris ex. Why caitlyn is slamming the former his. What you never knew about trump in miltrump in military s family tragedy that may have forced trump to quit drinking. Josh duggar and jared fogle are they sex addicts. Three signs your man may be living a double life. Whatever you hear is about 15 of whats really happened. Plus naughty news anchor. Patrick stewart outrageous new show, blunt talk. I did get to find out what motivating is. Now on extra from Universal Studios hollywood, the entertainment capita