The gun was a tool.  Take away the gun and force use of bombs and the tolls will be even higher.  Suicide bomber at the concert blowing up in the middle of a dense pack of people?  In the mideast these suicide bombers take out 50 at a time routinely.  Explosives are relatively simple to secure.  Or how about a semi accelerated to 70 mph and filled with water to add mass and punching power running into the weak wooden church.  Remember Oklahoma City?