Just poorly written.
If you take one of the Tweets showing the surveillance camera video and repeatedly hit the pause button from the beginning — you might have to try several times — you can see the collapse has resulted in the top floor dropping by about 1 story before the flashes start; AND there are flashes both on the top floor, and two levels below that.
Death toll in Florida collapse rises to 4; 159 still missing
https://apnews.com/article/florida-condo-collapse-285cbfbfca14594b6f69ff3301e7a487