In retrospect, that's an easy call to make. Elliot Rodger, based just on his publicized video and writings, was a time bomb and an omniscient, objective observer would have scotched his every attempt to acquire anything more dangerous than a cotton swab.
Of course, no such observer exists. Rodger was smart enough to glide past his brushes with the authorities, so he didn't trigger any of the legal tripwires that would have kept him from buying guns. The laws, and the law enforcement and mental health infrastructure supporting them, worked as well as anyone could expect. Rodger hid his agenda effectively enough that unless we investigated thoughtcrime, Rodger's unfitness to own anything more lethal than the aforementioned cotton swab could not have been discovered.
So I'm going to reject what I wrote a few days ago:
We will never be able to stop all those who are troubled from lashing out.To use the Isla Vista rampage as a rallying cry for greater gun control is a bad tactic. Rodger was a deeply, deeply troubled young man who was cunning enough to fool everybody tasked with keeping this sort of thing from happening. The kind of gun control one would have to advocate to prevent a rampage like Rodger's wouldn't be so much gun control as people control.
We might, however, be able to make it harder for them to hurt as many people as they can right now because gun ownership carries such low barriers.
Better gun control laws are sorely needed. However, even the best such laws would not have stopped Elliot Rodger. The only kind of "gun control" that would have stopped him would have been to make firearms illegal for private ownership. That may be your preferred solution, but it's a fantasy for right now.
I hope we get past the flawed, reductionist thinking that makes this rampage all about guns, and start asking ourselves about how we might intervene (without shredding our right to privacy, which I believe in even if certain far-right Supreme Court Justices do not) before the next Elliot Rodger comes along.