Police say a 2-year-old boy accidentally shot and killed his 11-year-old sister in their Philadelphia home while their mother was just down the hall in the bathroom.

Investigators say 11-year-old Jamara Stevens was killed when she and her three siblings, a 14-year-old boy, 7-year-old girl and 2-year-old boy, were playing with a .357 caliber handgun with an 8-inch barrel in their Mantuna home on the 3800 block of Wallace Street just before 10 a.m. Saturday.

Tiffany Goldwire and her four children were in her bedroom, when she went to use the bathroom, according to police.

At that point, the kids located the loaded firearm, which was left on top of the refrigerator by the mother's boyfriend who visited the home earlier that morning, and the eldest child retrieved it, according to reports.

While playing with the weapon, the 2-year-old boy pointed the loaded, cocked gun in the direction of his 11-year-old sister and it discharged, striking her in the arm, according to authorities.

Investigators say the bullet then traveled through her chest, hitting her heart.

The girl was taken to the Children’s Hospital of Philadelphia where she was pronounced dead at 10:20 a.m.

The surviving children and Goldwire were taken to police headquarters, where the mother was questioned for nearly five hours, according to reports.

After the family members were interviewed, investigators swiped them for evidence.

Sources tell NBC10 authorities determined the 2-year-old boy pulled the trigger because his arm had traces of gun powder and a burn from the blast.

Police say this is not the first time they have been to the Mantua home and that Goldwire is not cooperating with the investigation.

Detectives say they are trying to figure out who owned the handgun, which they found on Goldwire's bed.

After the shooting occurred, neighbors and relatives could be seen visibly upset outside of the Mantua home as members of CeaseFire arrived in the neighborhood to post signs calling for an end to shootings.

No charges have been filed as homicide detectives continue to investigate.