Along with the five guns, investigators also found a backpack of ammunition in the children's bedroom.

MONROEVILLE, Pa. (KDKA) — Two parents in Monroeville are facing charges after a 5-year-old boy accidentally shot and killed his 3-year-old sister.

The father is facing serious charges, including involuntary manslaughter. The mother is facing several charges as well, including endangering the welfare of children.

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On March 26, Martaz Colvin, Brea Sanders and their four children were inside their home at the Cambridge Square Apartment Complex in Monroeville when police say their 5-year-old son accidentally shot his 3-year-old sister, Braya Sanders, in the head with a 9 mm pistol, which was on top of the refrigerator.

The 27-year-old Sanders told police that she and Colvin were in the bedroom when they heard a loud bang. Sanders told law enforcement that she saw her son running to his bedroom saying, “No, I’m sorry, I’m sorry.” She called 911.

A neighbor who heard the shooting helped Colvin perform CPR. The 3-year-old girl was rushed to Forbes Hospital, where she was pronounced dead.

Sanders told investigators that the 29-year-old Colvin put one of the family’s three pistols on top of the fridge while the family was moving some of their belongings. Sanders believes the kids put a chair up against the fridge to grab the gun.

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Colvin told police that putting the pistol there was “his mistake.”

Detectives asked Colvin if he believed his youngest son could have chambered a live round and he said, “Yes, sir, I’ve seen him do it.”

Along with the five guns, investigators also found a backpack of ammunition in the children’s bedroom.

Gun expert Kim Stolfer said this accident could have been prevented.

“Leaving firearms around without any type of oversight is a huge mistake, and they can be misused,” said Stolfer, president of Firearms Owners Against Crime. “Keep the firearms unloaded unless you are ready to shoot it or take it out for carrying. Make sure you know who is around.”

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Police have not arrested the couple. A neighbor told KDKA’s Jennifer Borrasso that they moved out recently.