Personal traits can account for violent behavior. Psychologist Dorothy Ottnow Lewis found that murderous youths often suffer signs of:

Psychologist Dorothy Otnow Lewis found that murderous youths suffer signs of neurological damage and the neuroticism aggravated personality trait.

Explanation:

All right, Dorothy Otnow was a psychiatrist that studied violent behaviors and disorders related to them. She found out that very often, people who committed these atrocities had two singular characteristics. They had poor emotional control, and brain damage at a certain level. Now, she concluded that thy were connected and that one was the cause of the other. Meaning that organic failure triggered the poor emotion's control. Because the brain structure was not capable of development to achieve emotion control. Therefore, the subjects had strong neuroticism personality traits.

their just depressed and think that if they give pain to some one else the pain goes away from them. which it doesn't.