A 5-year-old boy in Pennsylvania was shot and killed Monday night by his 6-year-old sibling after they were left unsupervised in a room with an unsecured firearm, police said.

Allegheny County police responded to a Penn Hills home at around 5:30 p.m. and found the boy with a single gunshot wound, the police department said in a statement.

He was rushed to Children’s Hospital of Pittsburgh, where he was pronounced dead.

The statement said three children had been left alone in a bedroom with an unsecured gun.

“Detectives discovered evidence suggesting that a 6-year-old sibling accidentally shot the victim while handling an unsecured firearm present inside the residence,” the statement said.

The firearm is legally owned by a parent, who is cooperating with investigators, police said.

The Allegheny County medical examiner identified the child as Connor Wolfe. He attended kindergarten in the Penn Hills School District, which said Tuesday that it would have counselors available for students and staff members.

“We ask all members of our PH community to remember Connor and his family in your thoughts and prayers,” the district said in a statement.