Was Harless a criminal or victim of domestic violence and suffering from PSTD?

Question 1: If it is true that nothing could have stopped Harless from shooting the teacher and assistant principal, then how would you advise administrator to keep schools safe? 
Was Harless a criminal or victim of domestic violence and suffering from PSTD? 
Do you feel justice was served? Explain?
Question 2: Obviously the rules and policies made no difference is this situation, how can school officials prepare instructors and staff for emergency situations such as this one?