A 15-year-old Pennsylvania girl said she accidentally shot her ex-boyfriend in the head with a gun she stole as they were lying on his bed — and left him to die alone in his apartment, according to cops.

Precious Hamilton is facing charges of third-degree murder, involuntary manslaughter, possession of a firearm by a minor and carrying a firearm without a license in the death of 17-year-old Baseem “Seyven” Baker in Abington Township. Hamilton is being charged as an adult, the Montgomery County District Attorney’s Office said.

Cops responded to an unresponsive person call around 5 p.m. Monday at an apartment building in the 100 block of Old York Road. They found Baker dead from a gunshot wound in his bedroom.

According to a probable cause arrest affidavit, Baker’s mother said she left Baker and Hamilton alone in the apartment to run errands around 2:30 p.m. She returned around two hours later and was surprised the door was unlocked. After spending 30 minutes completing schoolwork, she found her son unresponsive in his bedroom and called 911.

The victim’s mother said Hamilton had been staying in the apartment with her son for the weekend. Detectives spoke with Baker’s cousin who was hanging out with the victim and Hamilton on Sunday evening. She said Hamilton pulled out a loaded “cowboy-style” firearm from her bag and showed it to them, according to the complaint.

Hamilton allegedly said she wanted to fire the gun out of Baker’s 11th story bedroom window but he talked her out of it. Instead, she “dry fired” the gun, meaning she pulled the trigger of the weapon while it was unloaded, cops said.  Investigators also found pictures and videos on Baker’s iPad of her holding the weapon, per the complaint.

Surveillance video showed Hamilton leaving the apartment shortly before 3:30 p.m. In an interview with detectives, Hamilton admitted to stealing the gun about two months prior.

Then she told cops her version of events. She said she and Baker began to “play around” in the bed when she decided she did not want to go any further, detectives wrote. She grabbed the gun from underneath the bed.

“Precious stated she produced the firearm in rapid fashion and was surprised when the revolver discharged, instantly striking Baseem and rendering him unresponsive,” cops wrote. “Precious stated Baseem fell off the bed onto the floor.”

She told cops she “panicked” and left the apartment without calling 911 or seeking help, the complaint stated. Hamilton called her mother to pick her up and they went home, the affidavit said.

An autopsy determined the manner of death was homicide, prosecutors said. Cops have yet to recover the firearm, according to the criminal complaint.