I guess our cohort who suggests that a man of firmness and virtue (I wonder if a woman could possibly be such an individual?) didn't take the time to watch the videos of the college students attempting to do just that and failing miserably. A few of them appeared to be of real firmness and virtue. Even the young lady who acquitted herself remarkably well failed to really have an effect on the situation.
I grew up in a very rural place in northern New England and used to hunt for food. When I was a hunter, the fish and game department rules for semi automatic weapons were that they could not have more then five rounds in the clip (or have a clip that held more than 5 rounds). I never needed more than two. Why anyone would argue they need a twenty/thirty etc round clip for any weapon used for hunting is beyond my understanding. If you can't take it down in under five you need to spend a lot more time at the range.
Sadly in this case no amount of gun control legislation would have solved the problem of keeping this individual from getting a weapon: he had no record of any kind to keep him from successfully getting any weapon he desired. Had he been properly treated for his mental illness he would have been much less likely to have felt the need to perform this heinous act and his mother would have known she had to keep those guns locked up, as all guns should be, away from the mentally infirm. Appropriate treatment would also have generated a record/paper trail that would show up in a proper background check keeping him from easily getting such a weapon.
Ultimately we will try and treat the effect and not the causes of this and all those other tragedies. Gun control is one of the answers, as in not having military grade killing tools all over (AK47 M16 etc related weapons).
Taking proper care of the mentally ill which requires not only a change in the care, but a change in the social attitude about such care, so those who need it will receive it, is a critical action on a national and state level to solve. This is not only a legislative change but a social engineering change so people who are clearly not normal or "right" need to be assisted by their families and the communities they live in, not leaving them to molder in homes or their apartments to descend into a madness the rest of us cannot understand or control.