According to police, the photo served as "a key piece of evidence" against Maxwell Marion Morton, who they say murdered Ryan Mangan, also 16.
A day after Mangan was discovered dead in his home on Wednesday, the mother of a third teen showed the picture to police, her son having screencapped the photo from Snapchat. From the Pittsburgh Tribune-Review:
"(Police) received a copy of the photo which depicted the victim sitting in the chair with a gunshot wound to the face," a police affidavit states. "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."
Additionally, police say the third teen received texts from Morton stating, "Told you I cleaned up the shells," and "Ryan was not the last one."
Marion reportedly confessed to the crime after police searched his home and found a 9 mm handgun. The teen now faces charges of first-degree murder, homicide and possession of a firearm by a minor.