The very unverified rumor I heard was similar to yours
@Van. Supposedly they were lifting something and it swung into the structure and knocked into one of the columns -- or something like that. Another also unverified rumor is that they were originally designed to have more structure be supported by concrete but at some
point VE'd to provide most of the vertical support strictly by structural steel columns.
Whatever the case, the building is probably a total loss and will need to be demo'd in its entirety. I wouldn't be surprised to see the project get scrapped along the way and see the developer fold and close up shop. The litigation on this will be ugly, and is likely to include exhibiting a video to a jury which has been floating around Facebook of a victim trapped under rubble. What appears to be metal framing wrapped itself across the waist and neck of the victim who at the time of filming was still alive under the rubble. Unclear if this is one of the survivors or the fatalities. This tragedy will haunt any further development of that hotel.