Oh I don't know, driving recklessly on a highway and causing a multiple vehicle pileup can cause that number of fatalities. And I doubt that most purchasers of assault rifles are doing so with the intention of killing 20-30 people in 3 minutes.

Though personally I cannot justify having either an assault rifle or a Ferrari, some folks just want these things for fun/sport (that's sport, not hunting).
I used to think it was terrible that life was unfair. Then I thought what if life were fair and all of the terrible things that happen came because we really deserved them? Now I take comfort in the general unfairness and hostility of the universe.