Law enforcement sources briefed on the investigation told ABC News that preliminary information developed in the probe indicates that the shooter was in the U.S. Army in 2008 and was "removed due to mental health concerns."
There it is…mental health, he also had no criminal record and had worked as an armed security guard (oddly enough).
That's 2 in recent memory that were in the service, discharged due to mental, and wound up legally purchasing firearms and killing a bunch of innocents.
That seems like something we could fix.