Brown had just finished his business of intimidating and shoving a little clerk around, burglarizing and getting away with it. I'd bet he was pumped about that more than the pot he'd smoked. He'd got away with it and his level of immaturity and limited intellect [and, ok, maybe the weed a little] told him to go for it again. Poor choice for him.
He finally wrote a check his body couldn’t cash, it was going to happen sooner or later.