The theory in this article is that the guy was about to abuse his daughter to death over an argument about drug use/dating, then changed his mind last minute and went to kill some random youths in a local dating spot instead. If it was an impulsive thing, presumably he didn't necessarily have time to choose the gun-enthusiast optimal weapon.
From the profile, he seems like the type of guy who would have stewed on what gun he would use to kill clandestinely in his free time. I mean he carried a pistol in each pocket on a daily basis.
