maurice dubois reports on the timeline of the shooting. >> we must have a strong president -- >> reporterscended on the butler farm show, about 100 acres used for agricultural exhibitions and a place where donald trump has appeared before. ♪ and i'm proud to be ♪ butler county voted overwhelmingly for trump in 2020. so this was expected to be as friendly a crowd as you'd find in the country. the former president and presumptive republican nominee took the stage at 6:03 p.m. >> hello, butler. and hello to pennsylvania. >> reporter: at about the same time a man was spotted on the roof of a building about 160 yards away. he was carrying an ar-style semi-automatic rifle. spectators alerted police. >> we noticed a guy crawling army -- you know, bear crawling up the roof of the building beside us. 50 -- 50 feet away from us. so we're standing there. you know, we're pointing -- we're pointing at the guy crawling up the roof. >> and he had a gun, right? >> he had a rifle. we could clearly see him with a rifle. absolutely. we're pointing at him. the police are down there running around on the grou

maurice dubois takes a closer look at the timeline. >> reporter: despite 90 degree heat, thousands descended on the butler farm show, about 100 acres used for agricultural exhibitions, and the place where donald trump has appeared before. butler county voted overwhelmingly for trump in 2020, so this was expected to be as friendly a crowd as you'd find in the country. the former president and presumptive republican nominee took the stage at 6:03 p.m. >> hello, butler. hello to pennsylvania. >> reporter: at about the same time, a man was spotted on a roof of a building about 160 yards away. he was carrying an ar-style semiautomatic rifle. spectators alerted police. >> we noticed the guy crawling army -- you know, bear crawling up the roof of the building beside us, 50 feet away from us. so, we're standing there, you know, we're pointing at the guy crawling up the roof. >> and he had a gun? >> he had a rifle. we could clearly see him with a rifle, absolutely. we're pointing at him. the police are down there running around on the ground. we're like, hey, man, there's a guy on the roof with a rif

. ♪ ♪ >> maurice: good evening, i am maurice dubois in for norah o'donnell.ing called the largest i.t. outage in history and it could affect your flight, your surgery, your deliveries, even your paycheck. and the cause, a faulty software update. millions of workers met with a blue screen of death when they turned on their computers today. airports across the country and around the world were packed with stranded passengers. planes were grounded by the thousands, not by the weather but by this technical tsunami. more than 4,000 flights were canceled around the world today, more than 2600 of them in the u.s. at atlanta's hartsfield-jackson international airport, the world's busiest, a quarter of all flights were canceled. we have team coverage tonight and cbs's kris van cleve will start off from the phoenix airport. good evening, kris. >> reporter: maurice, half of the cancellations affecting one airline, delta -- and the blue screens, we are seeing them here at phoenix sky harbor even as planes are moving again. late today, american saying it thinks it'll be a