My BS meter has pegged out on this one. First of all, the guy clearly had mental problems before the incident. Secondly, pot doesn't cause hallucinations unless there is another drug present (e.g., PCP), especially considering he admitted to only a couple of puffs. Besides, if he was smoking pot, he'd be too paranoid and lazy to kill.
I was also struck by the statement that pot use went up after the govt. relaxed penalties. A poster on another thread wouldn't accept my assertion that pot use here would increase if it was decriminalized, esp. if the price dropped as a result.