If he had been in the military, I think he would have had a lot more gear and more planning (he used CHAINS on the doors). It would seem unlikely that he would have been a psychological experiment if he had the drive to go to school. Most likely he just had a tragic family history that society's collective conscience doesn't want to own up to, so, society villainizes him endlessly instead of admitting the failures of all the security agencies that should have prevented the shooting.