Incompetence, gross negligence. No one, no matter how evil, is likely going to attach themselves to and pin their hopes on a week loser no talent mommy’s basement hack loitering gunman.
He did most everything right, from his perspective, save for his escape. His bullets killed and maimed. If he didn't have help, how did he get so much right, from his perspective, if he was just a weak loser no talent mommy's basement hack loitering gunman? Evil people recognized his potential and among their options, decided he was the one to be set up. Fortunately, he wasn't perfect, nor are the evil backers. They may be revealed yet.