As I said when we first discussed this, nobody deserves to be killed for a spat like this, but if anyone comes close to needing shooting, it's the bully couple. I think they taunted the guy over days, weeks, months until he simply snapped. They might have even lived if they hadn't continued to taunt him, even after they were shot and down with his gun pointed at them.
Bad decisions that ended in three deaths, but I still blame the couple more than the shooter for three people needlessly dying.