The Snohomish County Sheriff's Office said a 3-year-old boy is in serious condition after being shot in the mouth by another 4-year-old neighbor when they were playing with a gun, according to Reuters.

Lt. Susy Johnson says the 911 call came late Friday night after the boy's father heard a loud noise from the bedroom of their home in Lake Stevens, Reuters reported.

Johnson told authorities he found the door locked, forced it open and discovered the boy with a mouth injury, according to Reuters.

Johnson said he initially thought it was caused by the door striking the child, Reuters reported. The boy was flown to Harborview Medical Center in Seattle.

"It was determined that the three-year-old had a gunshot wound to the mouth," a statement said, according to Reuters.

"Initial information at the scene suggested that the four- year-old neighbor may have accidentally shot the three-year-old while playing, although the cause of the shooting is still under investigation," the statement added, Reuters reported.

When the child was examined at Providence Medical Center, doctors determined it to be gunshot wound, according to Reuters.

Detectives say the 4-year-old may have accidentally shot the 3-year-old, but that remains under investigation, Reuters reported.

Johnson said in a news release Saturday she didn't have any information about the gun or where the children got it, according to Reuters.