In Colorado, only a tiny fraction (about 1%) of people who have gun-disqualifying mental health histories have been reported to the National Instant Check System, where they could be discovered in a routine background check of a prospective gun purchaser. A felony conviction is also supposed to disqualify people from buying a gun, but only 40% of murder suspects have such a previous record of conviction.
The present national moment of grief and soul searching should not become another occasion for oversimplifying the problem of gun violence and laying the blame on any one thing -- "it's the guns" or "it's untreated mental illness" or "it's the information system" or "it's the violent popular culture in society." It may be all of those things. We need to address all of the variables and come up with smart evidence-based policies. Looking inside the killer's head should not be the first place to start.

Gun control won’t stop mass murder.
The conceptual problem is immensely difficult, especially in a society that is already as gun-saturated as America is today. The political problem borders on the impossible. Gun policy in this country is made by the National Rifle Association, and no serious effort at gun control can currently get past its veto.
Even when legislation passed during the Clinton years in the form of the Brady bill, requiring background checks at the time of gun purchases, or the assault weapons ban, the NRA succeeded in injecting gaping loopholes into the