There could have been two explosions. One from the RV and one inside the building.
Some people are saying that there was an explosion hazard sign on the building. It's possible that the RV explosion caused an explosion inside the building which could have been much stronger than the RV one.
There could have been two explosions. One from the RV and one inside the building. Some people are saying that there was an explosion hazard sign on the building. It's possible that the RV explosion caused an explosion inside the building which could have been much stronger than the RV one.
This seems to be the most likely outcome - which means that it was highly targeted and well-informed.