A Prince George's County police officer wounded a motorist yesterday in what the officer said was an accidental shooting, one that occurred after police confronted the motorist in the mistaken belief that he was driving a stolen car, sources said.

Late last night, county police shot and wounded two people, and two officers were injured, although they were not shot, said Capt. Andy Ellis, a police spokesman. All four were taken to local hospitals after the 11 p.m. incident in the Hyattsville area. The shooting injuries were not believed to be life-threatening, Ellis said. Police were still trying to sort out details of those shootings early today.

Last night's shootings were the fourth police-involved shootings in the county in three days.

Earlier yesterday, an officer wounded a man in the shoulder about 2:30 p.m. at Queens Chapel Road and Russell Avenue in Adelphi. Six hours after the incident, Ellis declined to identify the motorist or the officer who shot him or explain how the incident occurred. "The circumstances remain under review," Ellis said.

The man who was shot was in stable condition at Washington Hospital Center, according to police.

Police sources said the officer ran a computer check on the 1989 gray Toyota Camry and found that it was listed in a county database as having been stolen. That prompted the officer and two others to stop the motorist. The officers were undercover, driving an old, rusted, unmarked vehicle, sources said.

What led to the shooting remained unclear last night, but sources said the officer reported that his weapon fired accidentally.

Not until after the man had been shot did police look more carefully into the status of his car and learn that the Camry, though once stolen, had been found and recently given back to its owner, sources said. They said it was the owner who was shot.

The officer is one of 11 members of the department's new Auto Crimes Team.

The Adelphi shooting was the third by Prince George's police in as many days, prompting County Executive Jack B. Johnson (D) to reiterate his pledge to reform the department. Johnson, who prosecuted numerous Prince George's police officers for alleged wrongdoing when he was state's attorney, said he was left "uncomfortable" by this week's events.

"I'm concerned, very concerned," he said. "We're going to smooth everything out. One of the major issues of the campaign was to reform the police department. [The public] doesn't expect me to make it better in a week."

In the shooting late last night in the Hyattsville area, the two people were shot at 23rd Place and Amherst Road. After the shooting, they managed to drive about three blocks before they were stopped by another police car.

"I heard four gunshots. I was asleep, and it woke up everyone in the house," said Samora St. Firmin, 19, who lives on Amherst Road.

"Nothing ever really happens here. It's just a regular neighborhood. Kids play outside all the time," St. Firmin said. "I've lived here my entire life. Nothing like this ever happens."

The 1,400-member force led the nation in the number of fatal shootings per officer during the 1990s. But the rate has dropped dramatically since then. Last year, police officers shot seven people, two fatally.

Police have attributed the reduction to 18 months of department-wide retraining and the introduction of more nonlethal weapons to control unruly people.

The officer involved in the Adelphi shooting has been placed on paid leave pending an investigation.

Late Wednesday, Cpl. Charles K. Ramseur shot Desmond Eugene Ray, 22, of Forestville in the back as members of the department's narcotics unit tried to serve a search warrant at a Capitol Heights home.

Ramseur, 40, a Prince George's officer since February 1989, has been involved in three other shootings in the past 10 years, all of them ruled justified by police.

In March 1992, Ramseur shot and wounded a man who pointed a gun at him in Oxon Hill, according to police. He was cleared of wrongdoing.

A year later, Ramseur shot a man while responding to a robbery call at a Burger King in the Silver Hill area. According to an account of the incident, Ramseur heard shots fired, and when two suspects fled on foot, he and his partner gave chase and Ramseur shot one of them.

Ramseur received the Bronze Medal of Valor, one of the department's highest honors, for his "outstanding example of professionalism and police teamwork" for that incident.

And in June 2000, Ramseur wounded an unarmed man outside a Hyattsville pizza parlor after the man ignored orders to stop running from a fight, police said. The wounded man claimed that Ramseur overreacted and opened fire from inside his police cruiser. Although police acknowledged that the man was unarmed and had done nothing wrong, officers exonerated Ramseur, and a grand jury declined to indict him.

In the first shooting this week, on Tuesday, Sgt. Russell Watson, a 28-year member of the department, fatally shot Eric Stewart, 31, in the bathroom of Stewart's Landover Hills apartment. Police said Stewart was holding a knife to his mother's neck, threatening to kill her, and ignored orders to drop his weapon when Watson fired a single shot, striking Stewart in the head.

Staff writers David S. Fallis, Paul Schwartzman, Craig Whitlock and Clarence Williams contributed to this report.

Prince George's police investigate the scene of the third shooting by a county officer this week.