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 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. the trouble, with a type of airline ticketing technology. creating lines across the country. in las vegas, arriving on the monorail, seemingly endless lines. inside, passengers waiting everywhere in epic lines. with the work week about to begin, kayna whitworth is at l.a.x. nightmare for thousands as southwest airlines grapples with a computer glitch. the curb in las vegas and denver.

to shield passengers waiting from the heat. southwest blaming a "technology issue" affecting everything from its website to mobile app reservation centers and airports. >> sometimes murphy's law gets you, doesn't it? >> 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 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

southwest says the problem is affecting future bookings as well. i spoke with a woman who missed her flight and said no one could help her, because southwest has no access to their reservations. >> kayna, thank you. next to the race for 2016 and the big week for democrats. and vice president joe biden on the sidelines. his decision expected soon. cecelia vega on the vice president and the democratic race. >> 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

>> i'd be lying if i said that i knew i was there. >> reporter: sources now 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 9,000 people to a rally in colorado on saturday. 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

delaware weighing the political decision of a lifetime. and the clock is ticking. biden is expected to meet with his family at some point this weekend. that is going to be a deciding factor in his decision. he's here at his house in delaware through tomorrow. tom? >> thank you. and overseas now to that developing story in turkey. the devastating attack in a peace rally. this video capturing the act of terrorism as it happens. 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. 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.

wounded. 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 officials say they believe that it was suicide 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 and its kurdish enemies. tom? >> alex, thank you. and back to texas, and a police tasering incident captured on camera. the subject, a young city councilman. the officers asking him to step away. and then he's tased. 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.

>> okay, i'm not either. >> okay, man. go stand over there, man. this is a scene. this is a scene. come on. 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: police saying he physically resisted arrest. and mr. miller continued to do so despite repeated commands to stop. telling abc station ktrk the female officer who responded to over the summer. miller, charged with resisting public duties, now out of jail. he and neighbors, raising concerns over the male officer's use of force.

>> i don't see why he should have tased him. those officers still on the job tonight while the department investigates. marci gonzalez, abc news, new york. now to cleveland, prosecutors releasing two reports on the shooting death of tamir rice. both finding the police response, quote, "reasonable." it happened about a year ago, a squad car responding, within seconds shooting rice, who had a realistic pellet gun, killing him. tonight, the family's response, as the grand jury is still weighing charges. here's ron claiborne. >> reporter: the two outside experts retained by cleveland prosecutors looked at this evidence. and concluded the shooting of 12-year-old tamir rice was justified. it turned out he had a pellet gun. but a former fbi agent said, not

split-second decision, but his response was a justified one. the officer firing from close range in a matter of seconds. his conclusion, the officer was in a position of great peril. 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 family to submit their own reports from experts. they're still deciding. they do not trust that prosecutor. >> so many across the country following the case. ron, thank you so much. in florida, a dangerous and frightening sight.

in tampa bay, a water spout spinning at the side of a bridge, catching drivers by surprise. then the funnel cloud, crossing the road. 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 from their homes, as they battle a new enemy. phillip mena reporting in from conway, south carolina. >> reporter: with waters receding, the race to save the homes. >> you tear it all out. build it back. >> reporter: volunteers helping homeowners. as the city hauls away debris. the goal, getting the water-damaged drywall and furniture removed before mold starts growing. in the east, a much different story. here, in conway, the river is

and for the thousands living in far from normal. >> it's hard. they've never been through anything like this. >> reporter: trips to school, work, even walmart, require a 20-minute boat ride down the street. >> i wish we could make it all it go somewhere. >> reporter: and fema now bringing in amphibious vehicles to help. >> we've never experienced anything like this in our entire >> reporter: and tom, this is impassable. officials say it could take up to a month for the streets to tom? >> phillip, thank you. an exciting prospect in the fight against cancer, inspired by a trip to the zoo. a researcher there remembered that elephants rarely get cancer. and wondered if whatever

as well. 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 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

>> 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. >> we thank nick for that story. still ahead tonight, can the lottery be hacked? a lottery employee barred from playing. but investigators say that didn't stop him from helping others to 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 morning starts in high spirits but there's a growing pain in his lower back. as lines grow longer, his but after a long day of helping others, just two aleve have

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a former lottery official accused of being involved in a potential multimillion-dollar fraud. here's clayton sandell. >> reporter: what authorities call one of the biggest lottery frauds ever. tonight is getting bigger. edward tipton allegedly rigged commuter -- computers to pick specific numbers. but hid his own identity. paying associates to collect a $16 million prize. eventually, he was fired, convicted, 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 own brother and a longtime friend. they have not be charged in this

two counts of fraud in the earlier iowa case. >> 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's lawyer is appealing the conviction. and says the new charges are 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. >> thank you. coming up, could kanye west be moving to the white house?

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collision. the dodgers went on to win. weighing in on kanye west, who says he may run for president in 2020. country is going to elect a 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 where west was the headlining now to a hand-me-down sweater that just keeps showing up in one family's photos generation after generation. the grey sweater little brady gose is wearing here for his first grade picture has been worn by five family members in their first grade picture starting with his grandfather back in 1954. brady says he plans to pass it one day to his children. when we come back, the new trend in high schools. why the homecoming court is

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finally tonight, it's homecoming season. a tradition marked by the thrill of the big game, the dance and the crowning of the king or queen. but at some schools, the them -- memories will be 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. >> reporter: sarah neslun has down syndrome, but her sister says that's not why she's being

>> sarah didn't win because she it's because she's a great person overall. brayden carpenter, his date has >> reporter: in tennessee, brain cancer. he just wanted to make her comfortable. and this school, making a 3-year-old girl their queen. >> it's something that immediately touched us. there are so few times in your life when you feel an immediate impact. >> reporter: 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. her fighting spirit and the players' love for her, a true homecoming memory. >> 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 right back here tomorrow night. i'm tom llamas in new york.

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