Narcissism and a sense of entitlement commonly fuel people who commit mass shootings, says Brock University psychopathy expert Angela Book. 

“Often what you see with these folks, especially the young ones who do this, will have some kind of record of having said how famous they want to be, how they’re not getting what they deserve out of life; just being offended,” says Book.

The attention these individuals get following the shootings also motivates future acts of violence, says Book, adding that this occurs in a pro-gun environment.

“One of the most important factors in the rise of mass shootings is the gun culture in the United States,” says Book. “There is an almost religious viewpoint on gun ownership, and a sense that you are safer if you have a gun.”

Details are unfolding on Thursday’s shooting at Umpqua Community College in Roseburg, Oregon, in which at least nine people were reportedly killed.

Some media reports indicate shooter Chris Harper Mercer selected his victims on religious grounds.

“The target will often be someone who the shooter has something against, whether based on gender, religion, or cliques, in the case of high school shootings,” says Book. “That being said, they also usually want the fame. They are very narcissistic and entitled.” 

Book says people who commit such crimes could also be motivated by earlier experiences of bullying, being disadvantaged in some way, and often suffering from some form of mental illness, such as depression or psychotic symptoms.

“They end up in their own world, doing video games, that kind of thing,” says Book. “They get more and more isolated and they’ll start fanaticizing about it. It sort of spirals.”