Maxwell Marion Morton, 16, has been charged as an adult with first-degree murder, and allegedly confessed to police in the killing of 16-year-old Ryan Mangan in Jeannette, according to the Pittsburgh Tribune-Review.
Mangan's mother found him in their home on Wednesday.
Jeannette police arrested Morton on Friday after receiving a photo showing Morton with Mangan's body sitting in a chair, according to an affidavit.
Another boy allegedly received the photo from Morton via Snapchat and saved a screenshot of it before the picture automatically deleted, according to the Pittsburgh Post-Gazette. The boy's mother contacted police after learning he had a photo of the murder scene.
There was also a text message from Morton to the boy saying, "Ryan was not the last one," CBS Pittsburgh reports.
Investigators found a 9-mm handgun in Morton's basement as well as a spent casing from a 9-mm handgun, according to reports.
Morton, a junior running back on the Jeannette High School football team, has also been charged with criminal homicide and possession of a firearm.