A 39-year-old Gaithersburg woman was shot and killed and a 50-year-old school electrician was critically wounded yesterday afternoon in what Montgomery County police described as a murder-suicide attempt.

According to police, Alvin Gene Dorsey, of Frederick, Md., shot Gail Lorraine Sine several times as she was sitting in a car in the parking lot of a Gaithersburg apartment complex.

After shooting Sine with a hand gun, police said, Dorsey shot himself once in the chest.He was listed in critical condition yesterday at Suburban Hospital in Bethesda.

County police said that Sine and a woman friend were sitting in a car in the parking lot of the Emory Grove apartments at about 2 p.m. yesterday when Dorsey - who was an acquaintance of Sine's - walked up to tht passenger side of the car where Sine was sitting, and demanded she get out.

She refused, prompting Dorsey to fire a warning shot into the ground. He then fired at Sine several times before turning the gun on himself, police said. Dorsey collapsed as he tried to get back into his own car, which was parked nearby.

Sine was pronounced dead at the scene. Montgomery police said that charges against Dorsey were pending yesterday.

Sine's friend was not injured, police said.