Disgusting. Having said that I think the bulk of it was done by:
Anarchists from out of town
Local looters
You had the mother and stepfather standing around waiting for the announcement as though they didn't already know that Wilson wasn't being indicted. The announcement was made, the mother wailed on cue, the stepfather yells "Burn this mother down!" on cue, and they torch the Autozone.
There was no mob mentality. No one was killed** or seriously hurt, and no cops were shot, even though there was a good bit of gunfire.
** There was one death. A man named Deandre Joshua was murdered. The rumor is that he was a snitch who testified honestly to the grand jury.