Announcer this is nbc nightly news with lester holt, reporting tonight from the olympic summer games in rio. Good evening from copacabana beach on day one of the Olympic Games. The lights of the Beach Volleyball stadium blazing right behind me where the u. S. Women compete later this evening. Coming off a lavish Opening Ceremony celebrating the athletes and brazil, team usa was off to a great start today as a rookie from virginia took the first gold medal of the Olympic Games. But here tonight on the beach and in the pool is where some of americas best look to shine. Lets go about an hour from here to baja where we find nbcs Miguel Almaguer with the latest on the competition. Reporter lester, good evening. Olympic park is open for its first day of competition. Energy and excitement here is thousands are still pouring in to the venue. There are gold medal events later on tonight. It is a nightcap to an incredible day. Today against this stunning backdrop, the games began. The americans on the road. In the water. Shooting for gold. It didnt take long to reach the podium. 19yearold newcomer ginny thrasher, m im so overwhelmed. I cant express any emotions. Reporter the mens archery team also on target. Silver for team usa. With half a million visitors in rio for games were so pumped. It is so great here. Reporter this International Destination is brimming with national pride. This morning, a sea of yellow and green. After last nights dazzling the Opening Ceremony a tribute to brazils rain forest, the portuguese ships, the slave trade arriving in this country, a cauldron lit by a national treasure. And then an explosion of color for a country that never lost faith. Im so proud. I had goosebumps. I cried. United states of america reporter for team usa, Michael Phelps led the red, white and blue. Appearance at the olympics. Embodying the spirit of the games. The syrian refugee who swam for her life swam today in the 100meter fly. She won her heat but didnt advance. Still, she spoke with a heart of gold. It was an amazing feeling to be here and to compete here and see all the champions here. Yeah. It was special. Reporter but shell be back in the pool for the 100meter first full day of competition, the american stars are shining tonight. The defending womens soccer champs taking the field. For Kerri Walsh Jennings and april ross, their prime time debut at copacabana. A day to remember, and for some, a night theyll never forget. With all of the triumph here, there was also some heartbreak. A french gymnast broke his leg while finishing the vault competition. Audience knew it immediately as he was carried off. There was an incredible round of applause for him. All of this is still not only about the medals, but about competition. Miguel, thank you. Back in the united states, frightening moments at a concert last night when a railing suddenly gave way taking dozens with it and leaving more than 40 people injured. It happened near philadelphia as fans were dancing to the music of Rapper Snoop Dogg and wiz reporter moments before the collapse, cell phone video captured Rapper Snoop Dogg and wiz khalifa pumping up the crowd at their new jersey concert, turning their backs for just a moment, when suddenly the railing gave way. Sending dozens of fans slamming into the concrete floor five feet below, their bodies falling in waves. It was kind of like something in a movie. Something you would never see. It was just piles and piles of people on this popular event venue where eager fans were edging closer to rail hoping to snap photos of the duo. Until finally their weight pushed it over. Crowd rushed and when the crowd rushed the fence just couldnt hold it. Collapsed and people started falling. Reporter 42 people were sent to the hospital, one in critical condition. First responders built makeshift tents to treat injured fans lying on stretchers outside the arena. The concert canceled. Everyone on the lawn was like is everyone okay. You can hear people crying. Reporter snoop dogg tweeted late today prayers to my fans, wishing you all a quick recovery. With khalifa tweeting, i hope everyone at the concert last night is all right. Reporter the concert organizer live nation said it is working with authorities and Structural Engineers to determine the cause of the collapse. Fans took to social media saying, tonight was crazy. Scariest moment of my life. To bring fans together on a summer night. Those injured fans have since been treated and released from the hospital. Meanwhile, officials had already put in a new and secure temporary railing inside of this same venue where there is a concert being held tonight and where you can already see, there are some excited fans lining up behind me. Lester . Morgan radford tonight, thank you. Turning to politics and donald trump mending fences this evening. Hes in the swing state of New Hampshire tonight where polls after a bruising week of controversies and suffering rebukes of some within his own party, trump, it appears, is changing strategy. Jacob rascon has the latest. Reporter next stop, the granite state. Donald trump hoping for a rebound after a week of political whiplash. From lashing out at top republicans, to sudden unequivocal endorsements, telling the Washington Post on tuesday i like paul but these are horrible times. We need strong leaders then on friday i support, and endorse, our speaker of the house, paul ryan. Reporter from ive never been there with john mccain, he has not done a good job for the vets, to i hold in the highest esteem senator john mccain. Reporter and from senator kelly ayotte has given me no support, we need loyal people, endorse senator kelly ayotte. Shes a rising star. Reporter the aboutface, the cratering poll numbers, the fight with a gold star family, some true believers beginning to doubt. If he doesnt change, he may not win. We need to stay on this message and dont get sidetracked by what the media is saying. Reporter trump now back on message with a vengeance, his attacks on Hillary Clinton unprecedented. Shes a monster. The queen of corruption. Shes like an unbalanced person. Reporter Hillary Clinton also stumbling again on her emails. I may have shortcircuited, and for that, i will try to clarify. Reporter trump pouncing tweeting today anybody whose mind shortcircuits is not fit to be president. Look up the word brainwashed. Tonight trump returns to New Hampshire, the state that gave him his win during the primaries, plus a lot of mentioned, he is behind in the polls. Meanwhile, Bernie Sanders is targeting bernie or bust voters writing an oped in the l. A. Times writing, i voted for Hillary Clinton, and so should all of those who voted for me. Lester . Jacob rascon in New Hampshire tonight, thank you. In europe, authorities in belgium are investigating a machete attack on police today as a possible act of terrorism in a city outside brussels at a police station. Shouted god is great in arabic before wounding the two female officers. He was shot and later died. In syria, intense new battles on two fronts today, one a town held by isis, another a major city where a government siege has choked off hundreds of thousands of people. Chief Foreign CorrespondentRichard Engel is following it all and has our report. Reporter the scramble for territory is escalating quickly in the north, americanbacked rebels appear to be on the verge of taking the city of manbij. This video shows them helping civilians, mostly women and children, evacuate the wartorn city in a tunnel in a wall. Manbij is a major isis stronghold, a base of foreign fighters accused of plotting International Terror attacks. If it falls, it would be a major loss. A loss for isis. To the west, there is another rebel offensive, but very different. Islamist rebels are trying to break through the Syrian Government stranglehold on the city of aleppo. The rebels here released a highly produced video, aerial shots, music and all, showing their fighters in close combat and taking control, at least for a little while, on a Syrian Government military base. But who are these rebels . Some are from a group that just last week announced it is breaking its longstanding ties the rebels here are rebranding themselves and seem to be using this operation to show the world theyre fighting for aleppo, not al qaeda. U. S. Officials arent convinced they have changed allegiances at all. So many competing goals in syria, so many casualties, so many reasons this war has sent millions of refugees in to flight. Richard engel, nbc news. Back in the u. S. , many this evening as authorities hunt for a serial shooter now linked to nine attacks, most of them deadly. Now new concern that he is expanding his target zone. Jo ling kent has the latest. Reporter when the sun goes down in phoenix these days, fear comes out. The serial killer still at large, believed to have shot nine people, seven fatally, since march. It is certainly frightening for anyone. Reporter according to police, most of his attacks neighborhood, and now appears to be moving into central phoenix. While some residents are staying off the streets, many are still unaware of threats. You know about this guy . No. First time ive seen it. Reporter thats why this Guardian Angel walks a central phoenix neighborhood where the most recent shooting happened on july 11th. He doesnt care who hes shooting at. He doesnt care if there is a child in the car. Reporter this is not the first serial shooting for phoenix with its highways making it easy to escape. Still unsolved, a series of shootings last year, and a decade ago a shooter murdered eight people along baseline road in south phoenix. That killer now on death row. Retired homicide detective cliff jewel was the lead investigator on yet another shooting spree her ten years ago. He says serial shooters enjoy killing as a sport. I think hes having fun. Hes playing with the police. Game. And so far, hes winning. And hes going to continue to play this little game until he gets caught. Reporter the most recent shooting on july 11th happened right here in this neighborhood. And now police are hoping their new reward of 50,000 will entice anyone to come forward with new information to allow these people to get back to normal life. Jo ling kent, nbc news, phoenix. Still ahead tonight from rio and the olympics, a look at the rich and complicated history that frames this city and its were back from rio de janeiro. Were going to take you tonight beyond the olympics for a look at what gives life to this vibrant and diverse city of more than 6 million people. Stephanie gosk went out to see for herself what makes rio unique. Reporter there is no way to winding through the stunning landscape is a culturally rich and complicated city. In recent years, struggling with recession, corruption, and extreme poverty. But people here hold on tightly to what gives this city so much life. . . Reporter samba was created here at the foot of this rock. This is where the slaves they would express the culture of tradition with musical instruments, singing, dancing. Reporter two nights a week this little neighborhood still turns into an outdoor jam session. There is no separating the african roots from a brazilian. In a lot of ways, thats samba. Absolutely. There are so many Untold Stories and so many ways that they cannot express it. Street art like this is everywhere, made legal in 2009. They can put it on the walls to show the rest of the world, this is us, this is who we are. Reporter each mural shows deliberate attention to detail. That is not unique in this city. Watch how rios signature cocktail is made. Handmade. It has to be made in front of you. Amber took us for a brazilian before you can even take a bite, theres more coming. Just when i think ive made some progress, it starts to grow and grow. Theres nothing subtle about brazil. It is all extreme. Reporter that really goes for everything. Rio is bold and dramatic. For just over two weeks, it is on global display. A lot of that life happens right here on the beach. During the day people are running, playing volleyball, doinot im signed up for one tomorrow at 6 30, lester. You in . Tell me all about it. I would say there is an undeniable warmth to it. You look at that rich history even through all of their troubles, it comes alive. Stephanie, thank you. Still ahead, as this country deals with zika, the lastminute decision some women in the u. S. Although the zika outbreak has slowed hin it is mid winter, everyone here for the olympics is still aware of the threat, and many arent taking precautions. While in miami where the first locally transmitted cases in the u. S. Have just recently appeared, fear of contracting the virus is forcing some tough calls and decisions for many couples about whether to have children. More on this from sarah dallof. Reporter expectant mother Edith Mancini is putting as much temporarily with her 1yearold son to california where there have been no reported cases of transmission. Knowing that i can do something to possibly prevent it, why wouldnt i . Thats why we decided that i should leave. Reporter in the u. S. , 479 women have been reported with zika by the cdc. Due to privacy laws it is not known of any of miamis 16 homegrown cases are included in that number, but doctors in the city are fielding an influx of calls from pregnant patients and those hoping to start families. With so little known about zika and longterm effects, fear continues to spread. There is a lot of problems because there are so many gaps in the information. Reporter this miami clinic has seen an uptick in the women freezing their eggs in case they later contract the virus. I think its created a situation that makes patients very uneasy about her fertility, achieving a pregnancy or being pregnant in general. Theyre fearful. Reporter Vanessa Moore lives and works in the area where the local infections are suspected of occurring. She had her eggs harvested last week but is holding off implanting them until weather cools and the mosquito population drops. It is a decision that was probably made in the last 24 hours. Im really scared. I really am. Reporter no easy choices for those who want nothing more than a healthy pregnancan in miami, sarah dallof, nbc news. When we come back, the heroic effort by one american finally tonight, as every athlete here knows, it takes an almost super human effort to get to the olympics. Thats under normal circumstances. When a life threatening illness might seem impossible. But not for one determined American Woman who plays rugby. Heres hallie jackson. Reporter rugbys tough. Jillian potter, tougher. Not even a broken neck could stop her dream of making it on the rugby sevens team. New to the olympics this year. It was a broken bone. They were able to fix it. Like hey, you can play rugby again. Reporter the freak accident on field didnt keep her off it she would face her toughest opponent yet. Mouth cancer. Stage three. I was pretty naive about cancer. So when they discovered the tumor, i was like, okay, no big deal. Reporter the diagnosis coming just weeks before the 2014 cup. Potter played. I was like this is where my life changes. Yes. Reporter she started chemo, then radiation. When i starlo or my eyelashes and my body image started changing, i had to look in the mirror and i still had to smile. Reporter carol watched her wife fight before but never like this. Seeing the person you love most in the world battle something that you cant do much about is about as intense as you get. Reporter support came from jillians sport. The tightknit rugby sevens community raised almost 30,000 you can do it. You got it. Reporter last year, reading a poem, potter marked her final round of radiation. Her first practice back, not everything she hoped. So youre mad because even though youve got like top seven on the team, youre still upset i always want to have the best in the sport. Reporter no slack allowed with, for anyone. We are going after the gold medal. You cant have a standard less than that. You have to prepare yourself every day that youre going for gold. Reporter no matter the medal, potter already undefeated. Hallie jackson, nbc news, san diego. Thats going to do it for us on this saturday night from rio. Begins at 8 00 p. M. , 7 00 central. Among the events tomorrow, womens Beach Volleyball and swimming. Im lester holt. From all of us at nbc news, thank you for watching and an alert about medical marijuana in nevada. Why the state is warning some people are not following the law to get the medicine. A nervous start to the summer Olympic Games in rio. The bomb squad is called out near the finish line of a and cases of homegrown zee zika virus getting biggerrer. What experts say could spread the virus even more in america. A warning tonight from the state of nevada about medical marijuana. Dont believe claims that you can get medicalmileanhour