almost every school shooter's motive is unknown despite their mental health conditions and bullying they suffered

YEP, THEIR MOTIVE IS UNKNOWN; THIS IS THE PERSON WHO DID THE SCHOOL SHOOTING; THEY WERE BORN WITH A MENTAL DISORDER CAUSING BEHAVIOURAL ISSUES; YEP; THEY WERE BULLIED AT SCHOOL HENCE THE SCHOOL BEING TARGETED; THAT MAKES SENSE TO ME; SO THE MOTIVE IS BULLYING THAT WORSENED THEIR MENTAL HEALTH; THEIR MOTIVE IS UNKNOWN