After working as an expert in school shootings for the past two decades I have to disagree with the idea that school shootings are a gun problem or a bully problem. The world should have been able to see that after Josh Powell set his home on fire with him & his two children inside. There are many ways to kill if you are determined to do so.
There are prescription drugs on the market that produce both homicidal & suicidal ideation – which means the drugs produce ruminating thoughts of killing others or themselves coupled with ruminating thoughts of various methods of killing. Those medications are marketed as antidepressants.
The following is a link to a statement by Michael Moore after doing to movie Bowling for Columbine where they focused on the guns. You will see he has changed his mind about the guns & now knows it was the antidepressants that caused Columbine: