welcome to "world news tonight". system meltdown. hundreds of flights delayed. passengers standing in endless lines. tonight, the nationwide travel trouble. terror attack. the peace rally rocked by two powerful blasts. carnage and sorrow as officials point to suicide bombers. thousands now marching in protest. but who is to blame? caught on camera. a man on his knees, then police tase him. the man, an elected city councilman. and, inside job? a former lottery official, convicted for buying this winning ticket in iowa. his brother and friend also winning jackpots. tonight, the investigation going national. was your lottery rigged? plus, a possible cancer breakthrough. could elephants hold the key to beating cancer? the secret in their dna, and the new hope for saving human lives.

good evening. thanks for joining us on this sunday. i'm tom llamas. we begin with an airline travel mess affecting thousands of passengers. ticketing technology creating lines across the country. in las vegas, arriving on the monora monora monorail, seemingly endless license. with the work week about to begin, kayna when i wiitworth a. >> reporter: tonight, a travel nightmare for thousands as southwest airlines grapples with a computer glitch. lines spilling all the way to the curb in las vegas and denver tents set up in los angeles to

shield passengers waiting from the heat and a bottleneck in los angeles. southwest blaming a "technology issue" affecting everything from its website to mobile app reservation centers and airports. >> i think in 2015, i find it hard to believe that a simple system outage can be down for this long, without having a proper measure in place. >> reporter: the trouble beginning around 10:00 a.m. as southwest begins manually issuing boarding passes. by mid-morning, a tweet from southwest saying, "we apologize for this morning's technical issues." adding, 150 flights were affected. >> they took my name down manually on a piece of paper at the gate. which made me feel a little bit uneasy. >> reporter: with the airline scrambling, southwest employees handing out water to frustrated passengers. by 1:30 p.m., the number of flights affected jumping to 450. passengers unsure if they'd get to their destination. >> i'm still not 100% confident that i'm going to get on that flight. >> reporter: last month, american airlines grounded flights in three cities because of a computer glitch. in august, an air traffic control problem caused by a software update snarled travel along the east coast. and in july, united blaming a computer malfunction for hundreds of delays.

southwest says the problem is affecting future books as well. i spoke with a woman who said no one could help her, because southwest has no access to their reservatio reservations. >> thank you. and vice president joe biden on the sidelines of the democratic debate. cecelia vega on the vice president and the democratic debate. >> reporter: tonight, all eyes on joe biden. is this a man in the running? biden at his grandson's football game this weekend sprinting past the cameras. dodging questions about whether he plans to enter the race. >> everyone wants to know. >> get out of my way, will you?

>> reporter: after weighing the decision publicly for months sources tell abc news this is the week biden will make up his mind. a decision that will come after the first democratic debate on tuesday. on that stage, hillary clinton trying to maintain her status as the party front runner as her poll numbers dive. this weekend, she's off the trail and holding mock debates to prepare. her aides playing the role of her political rivals like former maryland governor martin o'malley and vermont senator bernie sanders. sanders gaining on clinton in the polls, pulling in nearly as much cash and drawing 9,000 people to a rally in colorado on saturday. this morning facing questions about whether he's trying to move away from his socialist label. >> when one of your republican colleagues gets on the show, do you say, "are you a capitalist?" have you ever referred to them as capitalists? >> yeah. are you a capitalist? >> no. i'm a democratic socialist. >> reporter: the big show now just two days away in las vegas. but the main attraction in this

race remains camped out in delaware weighing the political decision of a lifetime. and the clock is ticking. biden is expected to meet with his family this weekend. he's here at his house in delaware through tomorrow. tom? >> thank you. and to that developing story in turkey. the devastating attack in a peace rally. the event shattered by the first blast. moments later, a second one. then the bodies of the victims lay covered in flags. and tonight, this vital u.s. alla ally is in turmoil. alex marquardt with the story. >> reporter: youthful singing and joined hands under a clear blue sky. the peace this rally called for shattered by two blasts.

many fled as fast as they could. others stayed to help the wounded. the deadliest terror attack in turkish history. almost 100 killed. today, the site was cordoned off by police. forensics teams combing it for clues. this is as close as we can get to the scene. turkish ficials say they believe that it was suicide bombers who carried out the attack, either isis or kurdish militants. but so far, there has been no claim of responsibility. thousands turned out this afternoon for remembrances. and to vent their anger at the government for allowing the attack to happen. at the hospital, families and friends waited for news in the driveway. 21-year-old ulas was just a few yards from the blasts that took the lives of 16 of his friends. he's now worried turkey has entered a dark new chapter. do you think there will be more attacks like this in turkey? >> yes, yes, yes, it can be. >> reporter: as the country marks this tragedy with three

days of national mourning, that fear over more violence is now growing, with contentious elections just a few weeks away and turkey cracking down on isis on its kurdish enemies. tom? >> thank you. and back to texas, and a police incident captured on camera. the officers asking a young city councilman to step away. and then he's tazed. here's marci gonzalez. >> reporter: tonight, questions about this takedown of a texas city councilman tased by police in his front yard. >> put your hands behind your back. >> reporter: police body cam video shows councilman jonathan miller outside of his home thursday night, asking officers why they were questioning three of his friends. >> i'm not trying to be combative or anything.

>> okay, i'm not either. >> okay, man. go stand over there, man. this is a scene. come on. >> please don't put your hand on me. >> go over there before you go to jail for interfering. >> reporter: the tension, quickly escalating. >> i'm telling you one more time go over there before you go to jail. turn around. >> i'm not saying nothing. >> reporter: cell phone video repeatedly ignoring officers' demands to stop. >> reporter: the prairie view police chief telling abc station ktrk the female officer who responded to sandra bland. miller, charged with resisting arrest and interfering with public duties, now out of jail. he and neighbors, raising

concerns over the male officer's use of force. those officers still on the job tonight while the department investigates. marci gonzalez, abc news, new york. now to cleveland, police releasing two reports on the shooting death of tamir rice. it happened about a year ago, a squad car responding, within seconds shooting rice, who had a realistic pellet gun, killing him. here's ron claiborne. ï ¿>> reporter: the two outside experts retained by cleveland prosecutors looked at this security video of tamar rice's shooting. their conclusion -- the shooting of the 12-year-old boy was justified. it turned out he had a pellet gun.

in his report, a denver prosecutor dissected the video. the officer firing from close rang range in a matter of seconds. tamir's family, including his mother, outraged by the reports' findings. >> ms. rice and her family now believe that this has been an 11-plus month charade to ensure that's there's no accountability or indictment of these officers. >> reporter: a grand jury will ultimately decide whether to bring charges against the officers. but tonight, the rice family now skeptical. the prosecutor invited the families to submit their own reports from experts. >> so many across the country following the case. ron, thank you so much. in tampa, florida, a dangerous and frightening sight. a water spout spinning at the side of a bridge, catching

drivers by surprise. then striking a mail truck, tipping it over. the driver escaping without injury. and in parts of south carolina, a real-life water world. thousands of families forced away from their homes, as they battle a new enemy. >> reporter: with waters rece receding, the race to save the homes. volunteers helping ho inin inin. the goal, getting the water-damaged drywall and furniture removed before mold starts growing. in the east, a much different story. here, the river is now eight feet above normal.

and for the thousands living in the flood path, life is still for from normal. >> it's hard. they've never lived through anything like this. >> reporter: trips to school, work, even walmart, a 20-minute boat ride down the street. and fema now bringing in amphibious vehicles to help. and tom, this is one of those streets, still impassable. officials say it could take up to a month for the streets to dry out. >> phillip, thank you. an exciting prospect in the fight against cancer, inspired by a trip to the zoo. elephants rarely get cancer, and

wondering if that could help humans. here's nick watt. >> reporter: elephants have survived 55 million years on this earth. they've evolved to beat cancer. and they might just help us beat it too. >> in this elephant blood, i totally truly believe lies the secret to cancer prevention. we have something here that potentially can save millions of lives. >> reporter: elephant blood from schiffman's local zoo and the ringling brothers and barnum and bailey circus. you see, most humans have only two copies of a gene called p53, which kills cancerous cells. elephants have around 40. and elephants hardly ever get cancer. does then somehow involve getting p53 genes from an elephant into a human? >> that's one approach. there are other things we can do. looking for drugs that mimic the effect. >> reporter: schiffman is inspired in this bizarre collaboration by his patients. >> i'll undergo brain surgery again in two weeks. >> reporter: a recurring cancer because tony means has only one

working p53. >> i have passed it on, i guess, to landon, emma and sophie. >> reporter: whose lives one day could be saved by tonka, mabel, luna and assan. nick watt, abc news, salt lake city. still ahead tonight, can the lottery be hacked? investigators say a former official may be helping family members win. and later, dirty play? the bone-breaking slide the mets are furious about. those stories, coming up. today, jason is here to volunteer to help those in need. when a twinge of back pain surprises him. morning starts in high spirits but there's a growing pain in his lower back. as lines grow longer, his pain continues to linger. but after a long day of helping others, he gets some helpful advice.

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official is thought to have taken advantage of the system. here's clayton sandell. >> reporter: what authorities call one of the biggest lottery frauds ever. tonight is getting bigger. edward tipton allegedly rigged systems to pick specific numbers but hiding his own identity, paying associates to collect a $16 million prize. eventu eventually, he was fired, sentenced, and sent to prison. but officials say he also fixed games in colorado and wisconsin. a total of $1.3 million paid to winners that just happened to be his brother and a longtime friend. >> this is a breach of trust against lotteries, players,

games, and the billions of dollars at stake for the worthy causes that lotteries benefit. >> reporter: tipton is appealing the new charges, and saying it's an effort to garner publicity. but officials say they're not done. >> this is now a nationwide investigation. >> reporter: the lotteries say they've now added multiple layers of new security. hoping to lower the odds of getting taken again. clayton sandell, abc news, denver. coming up, taylor swift showing a super connection to her fans. what she did for one little girl that needed something to smile about. and why president obama says president kanye may not be a total fantasy.

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black guy from the south side of chicago with a funny name to be president of the united states? that's crazy. >> the president joking at a fundraiser in san francisco where west was the headlining act. and a dream come true for a taylor swift fan who's been having a tough time lately. 9-year-old prairie brolhorst, to the left of swift. meeting the superstar at a concert in omaha. just recently, prairie was diagnosed with a rare form of cancer and has undergone several surgeries. she and her family saying it was the best show ever. such a special moment. when we come back, why the homecoming court looks so different. it's now about life lessons on that special night.

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finally tonight, it's homecoming season in high schools across america. a tradition marked by the thrill of the big game, the dance and the crowning of the king or queen. and this year, we found some schools where it is about so much more. the school coming together to crown a queen unlike any other. >> she just has a kind heart. always wants to brighten people's day, and she does. sarah neslun has down syndrome, but her sister says that's not why. >> sarah didn't win because she has a disability. it's because she's a great person overall.

>> reporter: in tennessee, it his date has brain cancer. he just wanted to make her comfortable. and this school, making a 3-year-old girl their queen. the team first met her when they rehabbed her backyard, making sure she had grass to play in. she's undergone multiple open heart surgeries. >> it touched my heart, i wanted to cry, seeing her walk out being crowned queen. >> and it touched our hearts as well. "gma" first thing in the morning. david muir back here tomorrow night. i'm tom llamas in new york. have a great evening. good night. >> i'm here to talk about it

today. just grateful to be alive. alive, aearly buried man pulled from this collapse speaks with abc 7. a nailbiter that went into overtime, but the redskins could not get a win against the falcons. shakeup at the university of maryland, the school giving the head football coach the boot. 6:30, onbc 7 news at your side. the investigation into a crash that killed a motorcyclist in bethesda. roz plater is in bethesda with what we are learning. roz? roz: there are still a lot of questions about this crash.