Its going to be hard to prove the encouragement, because as far as I could see the issue with the can had been settled and squashed. They still said he'd get to do a run-in and have his spot with the wrestler... but beyond that I think its all on the dude who tried to kill someone.
And they didn't protect the guy who couldn't protect himself after they told the kid to "get receipts", making sure the kid understood what he meant, while amping him up to apparently "act" like he was going to fight? Sorry. They are responsible as well. I hope the victim sues the shit out of them and I hope he wins.
Sounds like the wrestler that invited him to attend was the guy telling him to get his receipt. Which he says he only said in character. He apparently has been friends with the Jackson family for years and is not the promoter. Sounds like the other wrestlers don't particularly care for that guy.
