Ever heard of the Bath School disaster of 1927?
http://en.wikipedia.org/wiki/Bath_School_disaster
44 dead, 58 injured.
Weapon: dynamite and pyrotol
At least those weapons are hard to come by for most.
Gasoline is still the #1 most “successful” mass murder weapon, it’s sold on every tenth street corner, costs about four bucks, and nobody thinks twice about anyone having it because most do.