Although mass murderers attempting to express their motivation in writing isn’t new, Northeastern University criminology professor Jack Levin said technology has changed the way that their messages are delivered. In the case of the Virginia Tech shooting in 2007, Seung-Hui Cho went to a post office and mailed videos to NBC, which eventually released them.

“Nowadays young people know enough about the Internet that they can do it themselves,” Levin said. “They can place themselves in a celebrity position without the help of traditional news sources.”

Levin said he worries that Rodger’s collective YouTube confessionals will set a new precedent: mass shooters making detailed videos.

Levin’s colleague James Alan Fox said mass murderers typically leave writings as a form of justification.

“It’s very important [to them] that the world doesn’t view them as some nut that killed for no reason,” said Fox, who has written several books on mass shootings. “In their minds, they are good guys.”