At this point, I would not rule anything out. It wouldn't have to have been Trump himself, or Barr. Any far right-wing group that supports Trump could have done it. At this point, it's just one person's opinion, based on experience working with those in the inner cities who are most likely to end up in gangs.
I'm not a conspiracy theorist, not by any stretch. But from what I have seen so far, in regards to sending in the unmarked troops and in regards to those who instigated violence during the protests, I'm willing to be open-minded enough to consider this an issue that needs to be investigated.