There were two drones, and the first clearly hit the dome. THe second which seems to be what everyone saw looks to have detonated over the top of the target area.
The blast looks to me like a small EFP, and since we've seen drones with RPG warheads as the payload, I'd speculate it was one of those unless better evidence presents itself. It looks like it was supposed to nose over and blow into the dome, and either detonated by position, or was command detonated early for some reason.
I saw no evidence of either a MANPAD or a gun system like a C-RAM/ZSU that would be used for Air Defense in a situation like this. The drones seem to have gotten there unmolested.