I agree that mental health is the linchpin in stopping this from happening-- every mass shooter had mental issues, including the Vegas shooter, who was on Diazepan- which causes paranoid and suicidal ideations, impaired memory and judgment.  Lazy elected officials and government do not have the courage to take this on, and are more than happy to instead blame the NRA.
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However, I take issue with your claim that "It doesn't matter wether he legally obtained a firearm." [sic]  It has everything to do with it, because it shapes the narrative AWAY from gun control legislation, and TOWARDS the mental health issue.  If Democrat and Leftist politicians would wake up and realize that the laws, regulations, and statues in place have NO affect on whether or not this man got a gun (he does NOT have the legal ability to get a gun), they should be then forced to take on the real issue-- the mental health aspect.