Personally, I hate guns, but if someone has a murderous intent they will find a way to carry it out, gun or no gun.
The worst school massacre in U.S. history occurred in 1927 in Bath, Michigan. Some whacko blew up half the school with dynamite and would have taken the whole place down if the second batch of dynamite had detonated. In all, 38 children died, along with 7 adults, and 56 people were injured.
No guns were involved except the rifle that he used to set off the dynamite in his own car which killed him and a couple of other people. Oh, and he had earlier beaten his wife to death and set fire to his farm, killing dozens of innocent animals.
Without a gun.
http://en.wikipedia.org/wiki/Bath_School_disaster