A 2-year-old boy fatally shot his 4-year-old sister at a Pennsylvania gas station Tuesday, authorities said.

The children were in a car parked outside the gas station at the Eagle Save Mart at Ninth and Kerlin streets in Chester, south of Philadelphia, when the incident took place. Police found the victim just before 11 a.m. ET, The Chronicle reported, citing a statement by Chester police.

An adult who was pumping gas into the vehicle rushed the older child to the hospital where she was pronounced dead, Philadelphia Inquirer reported.

Detectives believe the child had been handling a gun left unsecured inside the vehicle while the gun's owner was inside the gas station's mini-mart. It wasn't immediately clear what kind of a gun it was or exactly to whom did it belong. Chester PD Detective Rhaheem Blanden told NBC News that the children were siblings.

Delaware County District Attorney Jack Stollsteimer said that detectives from his office were assisting Chester police in the investigation of the "absolutely tragic" shooting. Stollsteimer said that everyone in the city and county was "just heartbroken to think of what happened to this poor child."

In March, a 12-year-old girl in Missouri fatally shot her teen cousin while the duo was playing with guns during a live stream video at a birthday party.

The young girl, identified as Paris Harvey, was making a live Instagram video in front of a bathroom mirror with her cousin Kuaron Harvey, 14, when the gun went off, killing the latter on the spot. Paris then shot herself. Arriving deputies found both the girls unconscious and not breathing. They were both pronounced dead at the scene.

Even as police had initially described the shooting as a murder-suicide, the family said it was a "tragic accident" that happened while the duo was playing with the gun at the apartment they had rented to celebrate birthdays. The family said that the gun went off when the duo was "trying to be too hip."

Representation. A gun. Pixabay