re: Would a deranged student be more deadly with a truck than gun?

"But he's not comparing it. His argument, as I see it (since I make the same) is that banning guns will simply result in these kids using another means to create mass casualties."

It's not much of an argument with school shootings, though, as compared to ideologically or religiously inspired terrorist attacks. School shooters are frequently into first person shooter games and suicidal as well as homicidal. Also, inflicting mass casualties with a vehicle is more effective in certain areas, such as the street parties in Nice, or heaven forbid, a mardi gras parade, but if what someone wishes to do is shoot people inside a school building, then they're going to need a gun, not a truck. To answer the specific question raised by the OP, the answer is that a deranged student could be very deadly with a truck, but not in most school settings.