The leftists can't miss the opportunity but nothing will come of it. First, the guy bought legally not for lack of laws but for lack of the government properly populating their beloved database. I believe that's been the case the last two times. Not one of these shootings would have been stopped by putting more laws on the law abiding. Funny how people bent on murder aren't particularly impressed by breaking gun laws too.
That said I am happy to finally see people addressing the real problem, mental illness. That one is a real sticky wicket. I have no idea how to deal with it without trampling all over civil rights, which is probably why everyone would rather attack the tool than the one who wields it.