Silence broken. Could you have prevented what happened to columbine . And tim tebow is here tonight. Hard to imagine he had trouble at the prom. Tonight, how hes helping thousands. Good evening. Great to have you with us on a busy friday night. Breaking news in the race for the white house. Donald trumps threat late today. The primary in South Carolina, donald trump saying he may sue ted cruz himself because he was born in canada. 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. 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 a woman trump tried to force to sell her home. 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 home. Theres more than a little irony in donald accusing someone 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. She got [ bleep ], she lost. Is anybody here worried about the frontrunning candidate shouting out obscenities in front of children . [ applause ] this is like what is going on . Off today during a forum at South Carolinas most conservative christian university. Theres a reason youre going to see four president ial candidates here talking to these christian conservatives here at bob jones university. In the primary here in South Carolina, twothirds of the voters here are expected to be evangelicals. We talked to folks on campus and found them more than a little concerned about trumps foul mouth. What about when you hear him swear . When he cusses or does dirty things that he doesnt, it just doesnt look christian. Reporter but today, heres Something Else for evangelicals to consider. This actress in a cruz ad hitting marco rubio . Maybe you should vote for more than just a pretty face next time. Reporter well, it turns out cruz dropped the ad when he found out. Carolina. Another big debate tomorrow night. Donald trump said he would stop swearing, tone it down, but tonight threatening to sue. Reporter yes, the stakes are especially high for ted cruz. 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. 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 the 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. Somebody called me on the phone. She said, reverend thompson . I said, yeah. She said, theres shooting around the church. And i just dropped the phone. Reporter 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. 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 president. 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 the commanderinchief. [ applause ] and reporter secretary clinton is convinced that wrapping her arms around president obama is a good strategy. But Bernie Sanders said he would be a better president with race. And lifethreatening cold moving in for 65 million americans, from the plains to the carolinas, subzero temperatures expected to shatter records. Heres linsey davis. Reporter tonight, the lake effect snow machine in full swing. Some spots in western new york getting more than three feet in 24 hours. 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 reporter in minnesota, firefighters already battling negative 10 wind chills. From the midwest all the way to north carolina, the National WeatherService Warning conditions will result in frostbite and lead to hypothermia or death if precautions are not taken. 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, frostbite can set in in just minutes. David . Linsey davis, thanks to you. Lets get right to rob marciano in new york tonight. Some temperatures not seen in 100 years . Reporter yes, were going to have to protect life and proffer professor property. Recordsetting stuff. Arctic air will be coming down, the peak of it will be sunday morning. These are actual low temperatures. 1 in new york. And look at the windchills, minus 21 in new york. 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. But first, we need to get through the cold of the weekend. Rob, thank you. In the meantime, breaking develops after a terrifying machete attack in ohio. Law enforcement saying he was known to the fbi. 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, hurt very reporter about 6 00 p. M. Thursday night, at nazareth restaurant. 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 the attacker went table to table. Authorities say he took off in a car, eventually tracking him down and shooting him dead. The attack leaving four people injured, including one critically. The fbi working with investigators trying to figure out a motive. Law enforcement says he was known to the fbi, but was not under a fullscare investigation. Tonight, new fears of a possible link to miscarriage with the zika virus. Two women suffering miscarriages when coming 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 now. 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 hondura 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. 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. Theres no confirmed connection to the miscarriages, right . Its not proven, but it is suggestive. Its likely, if it can cause some birth defects, it can cause others. And theres a new test . Yes, it will allow us to follow pregnant women and identify those at risk, and and now to a shooting in glendale, involving two teenagers. The school on lockdown. 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. The aerial pictures of the apparent parents and students evacuating are all too familiar. It was 17 years ago at columbine high school, and tonight, for the first time ever, Dylan Klebolds mother is breaking her silence. Heres diane sawyer wi her exclusive. The police were there and the 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 that god, stop this, just make it stop. Reporter and so her quest begins. Every year of her life with a magnifying glass. Looking for the path of her sons descent and the clues that she missed. 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 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. And i keep thinking 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. Why now . She says it took a long time to stare the truth in the face. Understand how she missed what she missed. And shes been talking to experts to try to make sure there may be something useful for another parent. A special edition of 20 20, a diane sawyer exclusive. Silence broken, a mothers reckoning, tonight at 10 00 p. M. Eastern right here. Up next, consumer investigation, a warning about something that could be in your garage right now. Our cameras under cover at discount stores. Could it be doing harm to your car . Also, the new headline involving the turf used by so many young athletes. 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. 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. Pneumococcal pneumonia. If you are 50 or older, 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. 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Reporter our expert 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 and that his engine died after he starting using the oil. I didnt think anything was different from any of the brands. 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 our standards for quality and value, but contain obvious and unambiguous language regarding the products intended 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. Thanks. When we come back, a surprise for one of our correspondents from the pope. And major news on Barry Manilow tonight. Well be right back. Yep, vern from voya. Why are you orange . Thats a little weird. Really . Thats the weird part in this scenario . Plook, orange money represents the money you put away for retirement. Save a little here and there, and over time, your money could multiply. See . Ah, ok. So, why are you orange . Funny. See how voya can help you get organized at voya. Com. Ibsd. You know the symptoms when they start. Abdominal pain. Urgent diarrhea. Now theres prescription xifaxan. Xifaxan is a new ibsd treatment that helps relieve your diarrhea and abdominal pain symptoms. And xifaxan works differently. Its a prescription antibiotic that acts mainly in the digestive tract. 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I want to fight for these people moreso than play football moreso than anything else in my life. Thats what i want to do. Reporter the tim tebow called the night to shine, prom night tonight for young people who otherwise wouldnt get the chance. 72,000 volunteers, 32,000 guests. In florida, getting ready for the prom tonight. Thank you for the flowers. Reporter just listen to colin. For him to come here to share all that with us i think he cares about us. Reporter in new york city, volunteers getting ready for tonight. I get so choked just thinking about it. Youre special and important. Lets have so much fun tonight, okay okay . [ applause ] reporter arm in arm. Walking them in. Ready for the dance. So many smiles, so many twirls. A night to shine for thousands. And so we choose all of the young dancers given the night to shine. The list starts now. Be comfortable on the job. Three ways to rock workout clothes without looking like a slob. Then why some couples are going all halloween for the love holiday weekend. Later, fast food joints have secret love potions. Our list of the best valentines drinks not on the menu. Im donna ruko. Lets start by counting down the three stories. Newsroom, here is bradley hasemeyer. Put you in the mood for valentines day after ten years, the incredible reunion with a