(CBS) — Nobody knows yet what set Adam Lanza on his murderous journey into that school in Newtown, Connecticut Friday.

And as CBS2’s Mike Parker reports, that includes Rush University Medical Center’s Chief of Adolescent Psychiatry.

“We’re reaching,” says Dr. Louis Kraus. “We’re trying to make sense of something we may never be able to make sense of.”

But Kraus says young people today are growing up in an increasingly violent media atmosphere.

Consider the video game called “Call of Duty/Black Ops II.”  The object of the game is for the player to kill as many opponents as possible.

“I have a strong concern over first-person shooting games,” Kraus says. “They’re designed to be addictive. Kids spend hours. There’s prior research to show that video games are associated with increased violent behavior.”

Today’s kids are also spending time with TV shows like “The Walking Dead,” where the goal of police is to mow down as many zombies as possible, including child zombies.

Zoe,  a 14-year-old student from Arlington Heights, says it can be a bit much.

“I think there is a lot of violence out there and that kids are getting kind of desensitized,” she says.

A tourist from Indianapolis, Leonora Kennedy puts it this way: “They play all these games, and it’s killing and hurting people on these games, and I think that’s maybe causing a lot of this stuff.”

Kraus says the American Academy of Pediatrics recommends no more than 2 hour of screen time each day for young people.

Watch & Listen LIVE