Your target freezes in place when he feels your gun. People move around, some sparing a quick look, but nobody says anything, least of all him. "You killed my sister," you say to him. "You tried to kill me."
"It ain't that simple," he begins, but you're not interested in letting him finish.
"Time to return the favor." You pull the trigger, blowing a hole in the man's side and killing him much more quickly than you feel he deserved.
Men, women, and children all stop to stare. The are gasps and screams and parents covering their children's eyes. With all the attention, you're quickly apprehended. You know you're going to jail at best, being hanged again at worst, but at least you took that bastard out first.