A one-year-old wild black bear, which weighed about 100 pounds, was shot and killed yesterday by police in Montgomery County after a four-hour search ended in the back yard of a Bethesda home, wildlife police officials reported yesterday.

The young male bear was cornered behind 6606 Lone Oak Dr. about 12:30 p.m. after a number of residents reported to police it was roaming the area. Officials said a decision was made to shoot it because in a populous area tranquilizing it could have been a risk.

"We were told there was a bear on the Beltway (Rte. 495)," said officer William Stallings of the Maryland Department of Natural Resources Police. "Before it was over there were a lot of police involved."

Maryland State police, Montgomery County police, Department of Park and Planning police and two officers from the Natural Resources police tracked the bear to the shrubbery-surrounded back yard as word spread around the street that there was, in fact, a bear in the area.

"First there was a rumor, but you kind of ignored it," said Robert C. Saloschin, a retired Justice Department lawyer who lives across the street from the house, unoccupied yesterday, where the bear was trapped. "Usually our neighborhood is limited to squirrels, rabbits and birds."

Police fired several shots from shotguns, killing the bear instantly.