It looked that way to me as well, and once a progressive collapse is in motion, it’s well, progressive.
But the forensics will evaluate everything, including the video evidence, and there’s plenty of concrete and rebar on site to test and evaluate. This will be the topic of discussion and study at ACI, ASCE, ICC etc. for quite a few years.
https://www.engineering.com/story/deadly-collapse-of-the-algo-centre-mall-roof
https://www.youtube.com/watch?v=2tO1L3SKhfU
Salty water is a dangerous thing to be dealing with when it’s just carbon steel and concrete that are the structural elements... This is a much smaller collapse but there are some similarities.