User blog comment:Speeddasher/I request a moment of silence/@comment-175.110.90.227-20120721120650/@comment-4703480-20120722170555

I think it was. One of the guys in an interview said that at first he thought it was a prank when the canister was thrown and at that the first shot was a firework, but then realised it wasn't, so I don't see any other possibilities.