Why They Kill.

The author looks at mass killers and what experts believe leads certain people to commit these crimes. The profile of mass killers looks similar to that of the clinical narcissist, along with a history of other emotional turmoil such as depression, substance abuse, or childhood trauma. Over half of mass killers had documented cases of extreme depression. They tend to disengage from people around them as they plan their assault and gain a fascination with firearms and weapons.