A 17-year-old girl stabs her sleeping father in the neck. She calls her boyfriend. She sends smiling selfies. She drives around town listening to music. She thinks she has gotten away with it. She forgot about the security camera in the living room.

In May 2024, 17-year-old Sierra K. was convicted of stabbing her father Robert Koons to death in their Pennsylvania home . The crime was captured on the family's security system, which first recorded her taking a knife from the kitchen and then showed the attack as her father slept in his chair . After the murder, she sent selfies to her boyfriend with messages like "I finally did it" and drove around with her friend Angel seeking vodka .

A second suspect, 19-year-old Victoria D., was driving the getaway car and was also charged, but charges were later dropped . Sierra pleaded guilty to third-degree murder and was sentenced to 12 to 30 years in state prison . Her lawyers argued she suffered from untreated mental illness . The judge said the case was "one of the most difficult" he had presided over but that no one who watched the surveillance footage could question her guilt .

Turn down the lights, put on your headphones, and press play because the camera was rolling the whole time—and the teenager smiling in her selfies had no idea.