A 6-year-old boy accidentally shot and killed himself in a quiet neighborhood of single-family homes in the Clinton area Monday afternoon, and Prince George’s County Police homicide detectives are considering filing charges against a 20-year-old who lived with the boy and apparently brought the gun to the house, authorities said.

Detectives and uniformed police officers descended on the 6000 block of Arbutus Lane about 2:40 p.m., cordoning off a long row of blue- and white-sided houses with yellow crime tape. Assistant Prince George’s Police Chief Kevin Davis said that they were exploring the tragic death of a 6-year-old boy, who shot himself in the chest with a loaded revolver that he found inside the home where he lived with his great-grandmother.

“This is every parent’s worst nightmare,” Davis said. “It’s our worst nightmare as well.”

While the criminal investigation is still in its early stages, detectives think that the 6-year-old found the revolver in a backpack belonging to a 20-year-old who also lived in the Arbutus Lane home. That 20-year-old, Davis said, does not appear to be a relative of the boy, and detectives are probing his exact relationship to the boy’s family.

Police detectives and officers led an older woman away from the scene Monday, and they put a handcuffed person into the back of a police car. Davis said that person was the 20-year-old, and that investigators were taking him to be questioned at police headquarters.

Police are still seeking answers to a myriad of other questions. Davis said that at the time of the shooting, the boy’s great-grandmother and grandmother were home, as were two girls, ages 9 and 11, who are also relatives of the family. He said the 20-year-old was not home but returned a short time later.

Davis said he was not sure exactly where the shooting took place inside the home, or whether the gun was legally owned and registered. He said investigators will probe all those questions as they consider whether to file criminal charges.

“This was an irresponsible act that caused this very, very unnecessary death,” Davis said. “This did not need to happen.”

Police did not immediately identify the boy, saying they were still working to notify family members.

A few neighbors lingered several doors down from where the shooting occurred, seeking information themselves on what had happened. Sonya Meadows, 47, a resident of the area since 1994, said she did not know the boy’s family, but the incident was disheartening.

“It’s really sad,” Meadows said. “A child that young, life just beginning and ending you might say in a matter of days.”

This Post has been updated.