A 20-year-old Falls Church man was fatally wounded by an off-duty Fairfax County police officer early yesterday after the man aimed a handgun at the officer, Fairfax County police reported.

Marwan J. Abosbitan of 1831 Olney Rd. in the Pimmit Hills area of Falls Church was pronounced dead at 2:30 a.m. at Mount Vernon Hospital.

Police gave this account:

Officer John Kirk, a member of the department since 1978, had gotten off duty at Groveton and was riding his motorcycle south on the 6600 block of Tower Drive in the Beacon Hill apartment complex when a car stopped abruptly in front of him.

Kirk fell off the cycle and then approached Abosbitan, the driver. Abosbitan drew a loaded .25-caliber automatic. Kirk showed his badge, twice identified himself as an officer and ordered Abobitan out of the car.

Abosbitan aimed the gun at Kirk and the officer fired several shots, hitting Abosbitan at least once. Abosbitan drove several hundred feet and collapsed.

A passenger in the car, Scott A. Tudge, 21, of the 1900 block of Jilson Street in the Pimmit Hills area, was hit by a bullet in the left index finger and was treated at Mount Vernon Hospital. Two other passengers were uninjured.

Kirk was placed on administrative leave pending an investigation.