Could be one of these, small enough to fit under the hood of a small truck, not even radioactive but vaporized an auto transport ship:
http://www.rense.com/general96/tianjinroro.html
SOF or weapons were staged in an unoccupied building owned by Vasquez?
How does Wells Fargo fit in?
How did SOF get to the building?
Tunnels? Abandoned streetcar lines?
How far from Staples Center?
What major Staples events or other conventions were about to occur?
What would justify such an operation? Major FF for sure.