Jed R. Bylsma, 30, of Gettysburg, Pa., was pronounced dead at the scene, police said.
Bylsma showed the trooper a Pennsylvania driver's license and said he was an officer with the Montgomery County Police Department, police said. The trooper "observed signs indicating the driver was operating under the influence" and called for backup.
Bylsma drove off from the stop and continued on eastbound U.S. 50 "at a high rate of speed," police said. The trooper pursued, and another trooper laid "stop sticks" on U.S. 50 at Airport Road to puncture the tires of Bylsma's car.
The vehicle struck the device, which deflated several tires, and rolled to a stop on the shoulder of eastbound U.S. 50, police said.
The two troopers gave repeated orders for Bylsma to exit the vehicle, police said. When he did not, they approached and found him unresponsive. They saw what appeared to be a gunshot wound to his head and a handgun near his hand in the center console of the car.
WUSA-TV reported that Bylsma had been an officer in the Montgomery County department since 2003 and was assigned most recently to patrol in the Silver Spring area. Police told the Washington station that he had been on administrative leave for about a year.
Bylsma's body was taken to the Office of the Chief Medical Examiner in Baltimore for an autopsy, police said. State police contacted Montgomery County Police. The incident remains under investigation.