And 17 years after columbine, one of the mothers of the shooters. Could you have prevented what happened to columbine . And tim tebow is here tonight. Hard to imagine he would have had trouble at the prom. Tonight, how hes helping thousands. Good evening. Great to have you with us on a very busy friday night. We begin with breaking develops in the race for the white house. Donald trumps threat late today. The primary in South Carolina, known for rough and tumble president ial politics. 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. 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 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 anyone of being nasty. Other rivals are now criticizing the billionaires tendency to do 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. Is anybody here worried about the frontrunning candidate 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 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 concerned about trumps foul mouth. What about when you hear him swear . When he cusses or does dirty things that he does, it just doesnt 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 allout brawl tomorrow night. 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 in particular, africanamerican voters. Who will have a major voice in deciding which of the two candidates gets the nomination. 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. 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 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 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 person to be the president and [ applause ] and reporter secretary clinton is convinced that embracing strategy. But Bernie Sanders said he would be a better president dealing with race. And word from the National Weather service that lifethreatening cold is 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 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 in minnesota, firefighters already battling from the midwest all the way to Weather Service is warning conditions will result in 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, frostbite can set in in just minutes. David . Stay in doors if you can. Linsey davis, thanks to you. Lets get right to rob marciano some temperatures not seen in 100 years . Reporter yes, weve had a couple of shots of cold air this but were going to have to protect life and property. Recordsetting stuff. The peak of it will be sunday these are actual low temperatures. Those two will be records. And look at the windchills, minus 21 in new york. Minus 30, boston. 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 machete attack in ohio. Law enforcement saying he was known to the fbi. That man, tearing from 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 how many people hurt . One seriously, we need an ambulance very badly. Reporter 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. Authorities say he took off in a car, eventually tracking him down and shooting him dead. Lone individual, machete, going into a public place. These 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. An alarming development, as we continue to report on the zika outbreak. New fears of a possible link to miscarriage. Two women suffering miscarriages and tonight, new word of a new 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 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. 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 to the miscarriages, right . Its not proven, but it is suggestive. Its likely, if zika can cause severe birth defects, it can cause other problems. And theres a new test . Yes, 80 of infections have no symptoms. It will allow us to follow pregnant women and identify those at risk, and should be here by mosquito season. And now to a shooting in glendale, arizona, involving two teenagers. The school on lockdown. A huge group of worried parents there gathering outside independence high school. 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 shootings. The aerial pictures of the parents and students evacuating have become all too familiar in this country. Its hard to believe it was 17 years ago, our nation watched the horror unfold in columbine high school. 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. 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 that god, stop this, just make it stop. Dont let him hurt anybody. Reporter and so her quest 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 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 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. 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. So why now . She says it took a long time to stare the truth in the face. Te ge back over her life, look at every part of it. She missed. What she failed to grasp, what she should have done differently. And shes been talking to experts to find 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. Diane, thanks. Up next, consumer investigation, a warning about something that could be in your garage right now. Our cameras under cover at some discount stores. 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 could you repeat country. And tim tebow is here tonight, putting football dreams aside to make dreams come true for thousands of children who 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. 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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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 i didnt think anything was different from any of the brands. Reporter glenn says its not just Dollar General selling 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. And new Health Concerns for well be right back. Vern from voya . 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. Do not use xifaxan if you have a history of sensitivity to rifaximin, rifamycin antibiotic agents, or any components of xifaxan. 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New robitussin 12 hour delivers fast, powerful cough relief that lasts up to twelve hours. New robitussin 12 hour cough relief. Because its never just a cough. At ally bank, no branches equals great rates. Kind of like grandkids equals free tech support. Oh, look at you, so great to see you none of this works. Finally tonight, tim tebow is here to help us name our persons of the week, young dancers who would have never had the chance to dance. America knows the tim tebow on the field. But tonight, what tebow is quietly doing off the field. More important than the magazine covers, are the children hes helped along the way. Tebow, born in the philippines, his parents missionaries. He was inspired by children with special needs, who simply needed a champion. Years later, hes now rolling out the red carpet. I want to fight for these people moreso than play football, moreso than anything thats what i want to do. Can i get a hug . Reporter the Tim Tebow Foundation sponsoring whats called the night to shine, prom night tonight for young people who otherwise wouldnt get the chance. 70,000 volunteers, 32,000 guests. 200 proms held in churches, 30 different faiths. 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 up even thinking about it. Youre special and important. Lets have so much fun tonight, 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. Thank you for watching. Im david muir. I hope to see you right back here on monday. Justice for this little boy. His father, Bradley Johnson was arrested tonight, accused of killing his sixyearold son. The woman who says she is the biological mother of riley talked with us. Reporter she says he was never filing so she cant understand what made him snap. Rachael johnson tells me that she still cant believe it is real. Sheet thinks that her son may have been killed because he was trying to protect the woman that her ex was trying to hurt. She wants everyone to remember and goofy child she knew. She showed these pictures of riley johnson. He had selfinflicted stab wounds and was found next to his father when police arrived. She has been trying to get her son back for all this time. Social services said they were here to protect my children and because of this, riley is gone. Reporter the coroner has not released the name of the little boy but again the father Brandon Johnson is still in the hospital recovering but he has been arrested and faces charges of firstdegree murder and sexual assault. Reporting live in arapahoe