Police say a Pennsylvania teenager fatally shot a 16-year-old classmate in the face and then published a selfie with the body on a smartphone photo application, the Pittsburgh Tribune-Review reported.

Maxwell Marion Morton, 16, has been charged as an adult with first-degree murder, homicide and possession of a firearm by a minor. Prosecutors are accusing him of killing Ryan Mangan, with whom he attended school in Jeannette, a Pittsburgh suburb.

The selfie was sent via SnapChat, a smartphone app that lets users send pictures that then disappear within a few seconds. The recipient of the photo allegedly sent by Morton, however, managed to save the file and forward it to authorities.

"[Officers] received a copy of the photo which depicted the victim sitting in the chair with a gunshot wound to the face," according to a police affidavit. "It also depicts a black male taking the 'selfie,' with his face facing the camera and the victim behind the actor. The photo had the name 'Maxwell' across the top."

District Attorney John Peck, meanwhile, called the selfie "a key piece of evidence that led investigators to the defendant."

According to the police affidavit, Morton confessed to killing Mangan after officers searched his home on Friday and discovered a 9mm handgun hidden under the basement step. The teenager allegedly also sent text messages that read, "Told you I cleaned up the shells. ... Ryan was not the last one."

Pamela Rutledge, the director of the Media Psychology Research Center and a psychology and social media instructor at Fielding Graduate University in Santa Barbara, California, said the selfie pointed to "a question about criminal pathology rather than technology."

"Perpetrators in need of validating their power and sense of self-importance have used all kinds of communications to 'brag' about criminal activities -- from the local hangout to social media, like Facebook," she said.

Rutledge underlined she was making general comments and did not know enough about the Pennsylvania killing to assess it specifically.

Roy Hall, the Jeannette High School football coach, said Morton had played "off and on" on his team.

"I'm shocked about the whole thing," Hall said. "It's hard to believe."