Live Updates: 51 unaccounted for after deadly high-rise collapse in Florida

"I mean, it is really, really traumatic to see the collapse of a massive structure like that.""Literally half of that building is not there anymore," Surfside Mayor Charles Burkett said.Rescue crews are continuing to look through the rubble for survivors."We've got the dogs, we've got the equipment, and we're going to do our very best to save as many people in that pile of rubble as we possibly can," Burkett said.Images from South Florida show the extent of the damage from Thursday's deadly collapse and the raw emotions felt by people in the area. pic.twitter.com/BGbRC7iSI9A man living in the Surfside, Florida high-rise building that collapsed early Thursday said he "thought it was lightning" when he first heard a crash outside his door."It was as loud as you could — the loudest thing I've ever heard," Barry Cohen told CBS News' Manuel Bojorquez. "It was rubble — gone," he said.Cohen said he was simply "happy to be alive."  Surfside, Florida Mayor Charles Burkett told "CBS This Morning" that roughly "one-third or more" of an apartment building was "totally pancaked" after it partially collapsed early Thursday."Looks like an earthquake," he told CBS News' Manuel Bojorquez.He described the grim prospects rescuers encountered in the middle of the night."They sent the dogs in, and there were just no hits. "We're all just scratching our heads trying to imagine what in the world could have happened."  Surfside, Florida resident Mich Balkany said the partial collapse of a high-rise apartment building in his neighborhood early Thursday was "absolutely insane.""I've been living in Surfside the past 10 years, and this is by far the most horrific thing that I've seen in my life," he told ReliableNewsMedia.CBS News' Manuel Bojorquez reported from the scene for "CBS This Morning."Balkany and his brother were taking an early morning walk when the building collapsed — and they have friends with family members living there."What we saw from the beginning was a huge cloud of smoke and lots of noise," Balkany said.His brother described the chaotic scene: "So we start rushing towards there, you know, we put our shirts over our face so we don't get any dust in our eyes and everything," he said. pic.twitter.com/w1B6CJGUNPOne man had got word of the partial collapse in dramatic fashion.He told CBS Miami he "was walking with my brothers, we were walking our dog in the neighborhood, and basically we heard a really big rumble and we thought it was a motorcycle, you know, and we turned around and saw a cloud of dust just coming our way."We were like — 'What is going on?'"We went rushing toward it with shirts over our faces and the security guard came out and we were, like, 'What happened?' and she said the building collapsed."Rescues of trapped residents are underway, and some may be caught in the rubble, reports CBS Miami.A man who lives in a building next door told the station he felt it."The building shook and then I looked out the window and you couldn't see.