Great to have you with us on a very busy friday night. We begin with breaking developments in the race for the white house. Donald trumps threat late today. The fight in South Carolina, known for rough and tumble president ial politics. Donald trump saying he may sue ted cruz himself because cruz was born in canada. The next showdown is 24 hours away. Jonathan karl leading us off. Reporter for a moment, it looked like wed be seeing a kinder, gentler donald trump. I wont use foul language. Im just not going to do it. Reporter trump is now taking his feud with ted cruz to a new level, tweeting this threat. If ted cruz doesnt clean up his act, stop cheating, and doing negative ads, i have standing to sue him for not being a natural born citizen. Cruz is pummeling trump with ads in South Carolina featuring this woman trump tried to force to vera cokings home was all she had left, but it stood in Donald Trumps way. Reporter what the ad doesnt mention the woman did not end up losing her house. Theres more than a little irony in donald accusing anyone of being nasty. Reporter cruz and trumps other rivals are now criticizing the billionaires tendency to do this. I would bomb the [ bleep ] out of them. I was going to say theyre full of [ bleep ], but i wont say that. She got [ bleep ], she lost. She said hes a [ bleep ]. Thats terrible, terrible. Is anybody here worried about the frontrunning candidate front of children . [ applause ] this is like what is going on . Reporter jeb bush sounding off today during a forum at South Carolinas most conservative christian university. Theres a reason youre going to see four president ial candidates conservatives at bob jones university. South carolina, twothirds of the voters here are expected to be evangelicals. Trumps foul mouth. What about when you hear him swear . When he cusses or does dirty things that he does, it just doesnt really look christian. Reporter but today, heres Something Else for evangelicals to consider. This actress in this cruz ad hitting marco rubio . Maybe you should vote for more than just a pretty face next time. Reporter well, it turns out shes a porn star. Cruz dropped the ad when he found out. And jon joins us from South Carolina. Another big debate tomorrow night. Donald trump said he would stop swearing, tone it down, but tonight threatening to sue. Reporter that gives you a sense of what i expect to be an allout brawl tomorrow night. The stakes are especially high for ted cruz. This is a state with a lot of the evangelical voters. He has to prove hes not just a onehit wonder that can only win in iowa. Jon, thank you. Meantime, on the democratic side, a fierce battle as well. In particular, africanamerican voters, who will have a major voice in deciding which of the two candidates gets the after the smiles last night, then the fireworks. Senator sanders, asked by the moderators if he could be standing in the way of history in this country. The possibility of the first woman president. Mary bruce in South Carolina with how he answered. Reporter tonight, Hillary Clintons new ad invokes the Horrific Church shooting in charleston, South Carolina, using the husband of a victim. Reverend anthony thompson. His wife Myra Singleton thompson was killed that day. Hillary is really committed to making sure that the guns dont get into the wrong hands. Reporter Bernie Sanders is channeling the pain of another africanamerican family. I was able to see my dad die on national tv. Reporter erica, whose father, eric garner, was killed by police. We need to believe in a leader like Bernie Sanders. Reporter both candidates battling for key africanamerican votes. At last nights debate, Something Else. Sanders asked if hes standing in the way of the first woman senator, do you worry at all that you will be the instrument of thwarting history as senator clinton keeps claiming . I think from an historical point of view, somebody with my background, somebody with my views, i think a sanders victory would be of some historical accomplishment as well. [ applause ] im not asking people to support me because im a woman. Im asking people to support me because i think im the most qualified, experienced and ready person to be the president and the commanderinchief. [ applause ] and reporter david, secretary clinton is convinced that embracing president obama is the right strategy. But Bernie Sanders said he would be a better president on race. And word from the National Weather service that lifethreatening cold is moving in for 65 million americans. From the plains to the expected to shatter records. Heres linsey davis. Reporter tonight, the lake effect snow machine in full blast. Some areas in western new york getting more than three feet of snow. Abcs indra petersons, in buffalo. Reporter its been a relatively mild winter so far by buffalo standards, but that is about to change. A dangerously cold arctic air mass is moving in tonight. Meaning by tomorrow morning we could set a 100yearold record. Reporter from the midwest all the way to north carolina, the National Weather service is warning conditions will result in frostbite and lead to hypothermia or death if precautions are not taken. I think its a very serious situation. Reporter the cold already causing damage. A burst pipe in scranton, pennsylvania, turning these homes into ice castles. In some places, it could feel like 40 below zero this weekend. And at temperatures like that, minutes. David . Linsey davis, thanks to you. In new york tonight. Some temperatures not seen in 100 years . Reporter yes, weve had a couple of shots of cold air this season. But this next one, were going to have to protect life and property. Recordsetting stuff. Huge trough in the east. Arctic air will be coming down, the peak of it will be sunday morning. These are actual low temperatures. 1 in new york. Minus 6 in boston. Those two will be records. And look at the windchills, minus 21 in new york. Minus 30, boston. Minus 36 in albany. Frostbite setting in just a matter of minutes in that case. What we dont need is a storm coming, thats what well get on monday and tuesday. It will start as snow in the big cities, but will change over to rain in the west. But first, we need to get through the cold of the weekend. Rob, thank you. In the meantime, breaking developments after a terrifying Law Enforcement saying he was known to the fbi. That man, tearing through the restaurant, then leading police on a highspeed chase. Alex perez with the 911 calls tonight. Somebody pulled out a machete and started stabbing people. Reporter tonight, investigators trying to figure out what triggered an attack in columbus, ohio. How many people hurt . One seriously, we need an ambulance very badly. Reporter beginning about 6 00 p. M. Thursday night, at nazareth restaurant. Police say the attacker, storming in with a machete in hand. I was on the ground, and i just thought to myself, at any moment ill get a knife in my back. Reporter she said the attacker remained silent and went table to table. Hacking at customers. Many defending themselves with chairs. There was blood everywhere. Reporter Authorities Say he took off in a car, eventually tracking him down and shooting him dead. Going into a public place. Those are the things that give us concern. Reporter the attack leaving four people injured, including one critically. The fbi now working with investigators here trying to figure out a motive. Law enforcement says he was known to the fbi, but was not under a fullscale investigation. Tonight, new fears of a possible link to miscarriage. Two american women suffering miscarriages when returning home. And tonight, new word of a new test you can take to check for the zika virus. Heres eva pilgrim. Reporter tonight, a new concern in the fight against zika. The cdc confirming two pregnant american women, traveling abroad, contracted the virus, then miscarried when they returned home. Our goal really is to protect pregnant women. Thats the key priority right reporter researchers already seeing a strong link between zika and birth defects of the brain. Now the cdc is looking at whether zika causes miscarriage. Samantha mejia was pregnant when she visited her husbands family in honduras before the travel warning. The biggest thing was knowing that i was pregnant and hearing all the different studies come out. Reporter when samantha came home, she tested positive for zika. She miscarried at nine weeks. The placenta also testing positive for zika. And his sister is pregnant right now, so were very concerned for her and her baby. Reporter david, this latest finding from the cdc highlighting just how little we really know about the zika virus. Researchers say theyre learning more every day. David . Eva, thank you. Lets get right to dr. Besser. Who spent years at the cdc. Theres no confirmed connection yet to the miscarriages, right . Its not proven, but it is suggestive. And its likely, if zika can can cause other problems. And theres news of a possible new test . Yes, 80 of infections have no symptoms. It will allow us to follow pregnant women and identify those who are truly infected, and should be here by mosquito season. Thank you, dr. Besser. And now to a Deadly School shooting in glendale, arizona, involving two teenagers. The school on lockdown. A huge group of worried parents there gathering outside independence high school. Waiting to take their children home. Students in shock. The girls were found dead, and a gun was recovered by their bodies. Both were 15 years old. Its unclear who fired or what the motive or plan was. Police are now suggesting no one else was involved in the shootings. The aerial pictures of the parents and students evacuating have become all too familiar in this country. Years ago, our nation watched the horror unfold in columbine high school. The student ecaping from the broken window. Students fleeing with their hand hands in the air. And the yearbook photos of the two gunmen. On the right there, dylan klebold. Tonight, for the first time, klebolds mother is breaking her silence. Heres diane sawyer with her exclusive. The police were there and the helicopters were going over. And i remember thinking, if this is true, if dylan is really hurting people, somehow, he has to be stopped. And that at that moment, i prayed that he would die. That god, stop this, just make it stop. Dont let him hurt anybody. Reporter and so her quest begins. She says, she goes back over every year of her life with a magnifying glass. Looking for the path of her sons descent and the clues that sometimes he would seem you know, distant or quiet. And i remember asking him, are you okay . Are you sure youre okay . You seem so tired. And hed stand up and say, ive got a lot of homework. I just, i need to go to bed. Reporter and you let it go. And i let it go. And thats the difference. If it were me today, i would dig and dig and dig. I felt that i was a good mom. That he would, he could talk to me about anything. Part of the shock of this was the was that learning that what i believed and how i lived and how i parented was an invention in my own mind. That it was a completely different world that he was living in. Reporter she says not a day goes by she doesnt think of the victims and their families. I just remember sitting there and reading about them. All these kids and the teacher. Constantly thought how i would feel if it were the other way around and one of their children had shot mine. I would feel exactly the way they did. I know i would. I know i would. And diane is with us now. 17 years have gone by. So why now . She says it took a long time to stare the truth in the face. To go back over her life, look at every part of it. Shes been on a quest to understand how she missed what she missed. Whrasp, what she should have done differently. And shes been talking to experts to try to find something useful for another parent. Hoping to prevent it from happening again. A special edition of 20 20, a diane sawyer exclusive. Silence broken, a mothers reckoning, tonight at 10 00 p. M. Eastern right here. Our cameras undercover at some finding a product sold at bargain prices, but could it be doing harm to your car . What to look for. Also, the new headline involving the turf used by so many young athletes. Children across this country. Many parents have been concerned about this for some time. And tim tebow is here tonight, putting football dreams aside to make dreams come true for thousands of children who would not have had the chance to dance. Well be right back. What if one situp could prevent Heart Disease . One. Wishful thinking, right . But there is one step you can take to help prevent another serious disease. One dose of the prevnar 13 vaccine can help protect you from pneumococcal pneumonia, an illness that can cause coughing, chest pain, difficulty breathing, and may even put you in the hospital. Even if you have already been vaccinated with another pneumonia vaccine, prevnar 13 may help provide additional protection. Prevnar 13 is used pneumococcal pneumonia. You should not receive prevnar 13 if you have had a severe allergic reaction to the vacyscitem, you may have a lower response to the vaccine. 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I go through periods where its hard to sleep at night, and stay awake during the day. Learn about non24 by calling 8448442424. Or visit my24info. Com. Next tonight here, a consumer alert. Abc news going undercover at some discount stores. Is there something on the shelves doing harm to newer cars . More than a dozen lawsuits filed. Heres gio benitez. Theyre almost sold out of it. Reporter abc news going undercover at Dollar General. 16 lawsuits claim the chain is misleading consumers by selling obsolete outofdate oil for cars without giving adequate warning. This is obsolete motor oil. Tom glenn of the Petroleum Quality institute of america spots this wellknown oil, 10w30. Its cheaper than the others. But look on the back. A warning. Not suitable for engines built after 1988. Thats 28 years ago. And heres another dg oil, 10w40. Theres that same warning on the back. Joe wood says he never thought to read the back of the bottle ngine died after he starting using the oil. I didnt think anything was different from any of the brands. Reporter glenn says its not just Dollar General selling obsolete oils. We go undercover to other stores. Out of eight other retailers, half were selling oils that glenn considers obsolete. Experts say if you want the most current oil, look for this starburst seal on the bottle. Older formulations dont have it. As for Dollar General, it told us their products meet not only value, but contain obvious and appropriate use. The company also takes issue with the term obsolete, saying these oils can be used in the millions of cars on the road built before 1988. Gio benitez, abc news, new york. And major news on Barry Manilow tonight. And new Health Concerns for children playing on artificial turf. Well be right back. The orange money retirement rabbit from voya. Vern from voya . Yep, vern from voya. Why are you orange . Thats a little weird. Really . Thats the weird part in this scenario . 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The historic meeting between pope francis and the head of the Russian Orthodox church, the first such meeting in almost 1,000 years. And our terry moran, blessed by the pope on the plane. An unexpected honor. And breaking news on the artificial turf used on athletic fields. Socal