An American teenager who allegedly murdered a classmate was caught by police after he sent a Snapchat photo of himself posing with the deceased to another student.

Maxwell Marion Morton sent the sick selfie to a friend, who grabbed a screenshot of the offending picture which his mother submitted to US police. It is said to depict Marion Morton with victim Ryan Mangan in the background. In the image, Mangan has gunshot wound in his face.

Prosecutors will be using the Snapchat as "key evidence". "[Police] received a copy of the photo which depicted the victim sitting in the chair with a gunshot wound to the face," states a police affidavit.

"It also depicts a clack 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."

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The suspect also allegedly sent text messages to his friend, writing "Told you I cleaned up the shells." Another revealed that the suspect was likely to kill again. "Ryan was not the last one," it said.

Maxwell Marion Morton confessed to the killing after police also found a 9mm handgun in his home. He will be tried as an adult.

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