A 15-year-old boy was fatally wounded in the head yesterday when a flare gun went off in the bedroom of his Mount Vernon-area home.

James Leon Cornbrooks and two other boys were in the room when the gun -- apparently loaded with a shotgun shell rather than a flare -- discharged, blasting the left side of Cornbrooks' head with pellets at close range, according to Fairfax County police.

Police said they didn't know last night to whom the gun belonged or exactly how it went off. They said their investigation was continuing.

The shooting at the boy's home, 2204 Bassett St., occurred about 5:30 p.m. Cornbrooks was pronounced dead about an hour later at Mount Vernon Hospital.

Donald E. Oglevee, the boy's step-father, was in another part of the house at the time of the shooting. A neighbor said the boy's 13-year-old sister ran into the street screaming when her brother was wounded.

Cornbrooks, a sophomore at Fort Hunt High School, was recalled by neighbors as playing baseball in the circle at the end of the street. He often would help his sister deliver The Washington Post.

As detectives inside the house were trying to piece together the shooting late yesterday afternoon, one of the teen-aged boys who was in the room at the time of the incident walked outside into the cold drizzle, visibly shaken.

"It was just one of those stupid, stupid things that never should've happened," he said.