The criminals are hiding in plain sight.
We are wasting time talking about guns and violent videos. Antidepressants are the culprits.
They are one of the common denominators in almost every mass shooter going all the way back to the Columbine kids. By the way, these people do not need to use guns; they sometimes use a bathtub to kill. Remember Andrea Yates of Houston who killed her children by holding them underwater one by one in the bath tub on June 20, 2001? She was on antidepressants.
Other common denominators: They frequently commit suicide immediately after the homicide.
One does not need to be a medical genius to notice all of this. Simply watching TV commercials for antidepressants gives us the information that we need in the form of the listed side effects: hostility and thoughts of suicide among others.
Charges should be filed against the drug manufacturers and the prescribing physician, perhaps even the drugstores that fill such prescriptions. Civil suits could follow.