70 % of the perpetrators of school shootings were under the age of 18 , with the median age of 16 . More than 85 % of the perpetrators of school shootings obtained their firearms from their own homes or from friends or relatives . Targeted school shootings , those occurring for example in the context of a feud , were about three times as common as those that appeared indiscriminate . Most perpetrators of school shootings exhibited no signs of debilitating mental disorder , such as psychosis or schizophrenia , although most mass killers typically have or exhibit signs of depression . On the other hand , Eric Harris was almost certainly a psychopath as noted by the FBI . Between the 1999 Columbine High School massacre in Colorado and 2015 , " more than 40 people " were " charged with Columbine-style plots ; " almost all were white male teenagers and almost all had studied the Columbine attack or cited the Columbine perpetrators Eric Harris and Dylan Klebold as inspiration
Columbine High School massacre
Columbine High School massacre
School shooting