It all seems a bit weird. His indictment wasn't published, probably to protect informants or UC's. He was unarmed and there was no weapon found at the scene, just a few rounds and magazines. There was supposed to be an investigation of the shooting, but nothing ever came of it.
Yup this is typical BATFE / FBI shenanigans. They don’t have anything to charge him with so they just make shit up. I’ll tell you something else don’t be surprised if this guy says he did not own that stingball. It’s quite possible when no weapon was found at the scene then suddenly a contraband stingball magically appeared. Keep in mind these are devices used almost exclusively by law enforcement such as the BATFE.