A 4-year-old girl shot dead her 4-year-old cousin with a rifle that she found while playing at her grandfather's house Thursday in Detroit.
Police said the "tragic accident" was a case of irresponsible gun ownership but have not yet made any arrests.
The girl shot the boy on Thursday afternoon at a home on the city's west side, Detroit Police 3rd Deputy Chief Rodney Johnson told NBC News.
"This is a tragic, tragic accident, and it could have been avoided," Johnson said.
The children were visiting their grandfather but had been left in the care of a family friend when the incident happened, Johnson said.
Emergency services were called at about 4:35 p.m., and the boy was taken to Henry Ford Hospital, where he died.
Police are still investigating and have not ruled out charges.
The Detroit Free Press reported that the girl found the gun loaded and not locked in a case underneath the bed. Johnson described the weapon as a "long rifle" but could not confirm where the girl had found it.