A teen is accused of killing his girlfriend during a hike.

Julianne Siller, 17, was stabbed in the throat and body Saturday night by boyfriend Tristan Stahley, 16. Authorities could not determine how many times Siller was stabbed a the attack had been very brutal.

The incident happened at a hiking trail in suburban Philadelphia. The couple, who had been dating on-and-off since January, reportedly got into an argument over Siller "going out too much", according to investigators. Siller allegedly smashed Stahley's phone. He reacted by pulling out a knife with an orange handle before he stabbed her multiple times in the throat and body.

Investigators say the16-year-old then dragged the body off the hiking trail and into the woods to cover up the murder. He then went home, covered with blood and dirt on his legs.

Stahley's mother Heather Stahley told investigators that it looked as if he had been crying. He would not explain anything when she asked him what was wrong. Instead, he said he will tell her if the two went for a walk.

During the walk, he reportedly confessed to his mother about the crime and when his mother asked whether it was a joke, he said "no" before crying hysterically.

Siller's body was discovered after his relatives called police.

Stahley has been arrested and charged with one count each of first-degree murder, third-degree murder and criminal possession of a weapon.