I don't think it is likely that a mental health evaluation would have demonstrated much. The law only bars those who have been involuntarily committed from gett

I don't think it is likely that a mental health evaluation would have demonstrated much. The law only bars those who have been involuntarily committed from getting firearms, a diagnosis of mental illness is not sufficient. And an involuntary commitment is a pretty high bar. My Dad is a clinical psychologist who evaluates people for the courts, and he can go on and on about how the severely mentally ill often do not qualify for involuntary commitment. Unless you are actively trying to hurt yourself or others you will not be committed, which basically limits it to people who are either attempting suicide, or assaulting people. I'd also like to point out that there are a number of issues with the current system besides what you've mentioned that could improve things. For starters, even if this person was involuntarily committed, he would fail a background check, but would still be able to purchase guns online or at a gun show without a background check. There are red flag laws, which allow people to petition the court to temporarily seize guns from someone acting in a disturbing way, which would have been ideal for this case, but these are only in some states.