The situation began about 2:30 p.m. when Barnard pulled over the driver of a 1997 Saturn for speeding on eastbound U.S. 40, about four miles west of Clear Spring, Betts said.
In the car were a male driver and a female passenger, Betts said. Barnard ran a check on the driver's license and registration, and determined that he was wanted on open warrants, Betts said.
Barnard, following state police protocol for wanted suspects, requested backup, Betts said.
When Weaver arrived at the scene, both troopers approached the vehicle, he said. The female passenger got out without any problems, but the driver refused to get out, Betts said.
Weaver saw the driver pull a semi-automatic handgun from his waistband, Betts said.
"In fear for his and his colleague's lives, Cpl. Weaver drew his department-issued pistol and fired at the driver," Betts said.
Police would not confirm the number of shots fired, Betts said. Weaver fired from just outside the rear of the car on the driver's side, he said.
The troopers administered first aid until an ambulance arrived to take the man to the hospital.
The female passenger, Christine M. Younker, 47, of Warfordsburg, Pa., was taken to the Hagerstown barracks to be interviewed, Betts said.
U.S. 40 was closed between exit 9 of Interstate 70 and Funkhouser Road near Clear Spring until about 7:30 p.m. while police investigated.
Based on the preliminary investigation, there was no indication of wrongdoing on the part of the Maryland State Police, Deputy State's Attorney Joseph Michael said in a statement.
The Washington County State's Attorney's office will wait until the investigation is complete to make a final determination, Michael said.
Members of the Maryland State Police Homicide Unit, Hagerstown Barracks, Forensic Sciences Division, Crash Team, Internal Affairs Unit and the State's Attorney's Office were conducting the investigation, Betts said.
Weaver is a 12-year veteran of Maryland State Police and Barnard is a 14-year veteran, he said.
Jessica Dunn, owner of Indian Springs General Store, said she saw the scene through the window of her store. It started out like a normal traffic stop, she said.
"I saw one cop car, then I happened to be walking by the window again and I saw both of the cop cars," Dunn said. "That's when I heard the shots."
Dunn said she saw one of the troopers firing into the open door of the car and heard three or four shots. The trooper was close enough to touch the driver, she said.
At least 20 police cars arrived at the scene after the shots were fired, Dunn said.