Agreed that guns don't kill people, people kill people.
But guns do make it rather easy to kill.
I doubt strict gun control would prevent such all mass killings of random people. People who want to kill many people randomly, and have time to plan an attack, have many non-gun methods of killing others.
But strict gun control, to the point where almost nobody could legally carry a gun everyday without it being a crime, would probably do wonders for simple, stupid killings where someone gets pissed.