[taxcontrol]

He was arrested, convicted and had some community service to do.

But

Since it was a misdemeanor assault charge and not punishable with 2 years in prison, never was reported to NICS.

[RC one]

The thing that most of these mass shooters have in common (most, not all) is that they are at that age when schizophrenia symptoms typically start to manifest-right about the time it becomes legal to purchase a firearm. I believe that's a common reason for why they seem to slip through the cracks. They just haven't had a chance to show us their true self yet and when they do break, it can be dramatic. You add all the stress associated with being that age, the testosterone, and maybe some drugs, and BAM, you get an emotional explosion like this.