Could not have been that bag that exploded.
Look at how the silver crowd control fence that the bag is leaning against is behind it in the “before” photo.
Now look at how that fence is bent forward and to the right, into the mail box, in the “after” photo.
An explosion in the bag would not bend that fence in that direction.
Rescuers and witnesses moved the barriers to help victims! Also, second photo taken an hour or more after first.
Well the experts will sort this out. You can't necessarily predict where things will land in explosions and I would not necessarily rule anything in or out