Lack of Consequence can be a factor. Bullies in school are not punished severely for their bad behaviour. They thrive in a culture where the consequence of their action is a mild reprimand and detention. Sometimes they are made to write a note of apology to the victim; very often dictated and not sincere. Parents very often do not believe their kid is guilty, so there is rarely a follow up after school, or re-enforce the teachers authority.

Some people have trouble accepting that there are evil people who enhance their reputations in the gang by killing for no apparent reason. In some gang culture you must be blooded (kill) before you are accepted. Not too long ago a gang called Einsatzgruppen became very efficient killers. September 1941 33,000 men, women, and children were shot and buried in a ravine at Babi Yar in just two days.