A Prince George's County police officer fatally shot a man during a traffic stop in Laurel yesterday after the suspect allegedly fought to avoid arrest, punched the officer in the head and pulled a knife, authorities said.

Police said an officer, responding to a nearby emergency call, had tried to stop the man, identified as Howard Robinson III, 27, of Laurel, after he ran two red lights on Route 197 and passed several other police cars responding to the same call.

Instead of stopping immediately, police said, Robinson drove into the Montpelier Woods apartment complex and came to a stop in front of his home in the 9400 block of Muirkirk Road. Robinson then got out of his car and tried to run away, police said.

Prince George's police spokesman Royce D. Holloway said the officer chased Robinson into the stairwell of his apartment building, where "a violent struggle ensued," during which Robinson pulled out a knife with a five-inch blade. The officer then shot Robinson twice in the upper chest, police said.

Police said the officer and a nurse who witnessed the shooting tried to administer first aid before paramedics arrived. Robinson was taken by helicopter to Prince George's Hospital Center, where he was pronounced dead about 11:15 a.m., Holloway said.

Police officials declined yesterday to identify the officer who shot Robinson but said he is a 10-year veteran of the force assigned to the Bureau of Patrol. The officer was taken to Laurel Regional Hospital, where he was treated for minor head injuries and released. He was placed on routine administrative leave pending an investigation of the shooting, police said.

Police said they were trying to determine what sparked yesterday's violent confrontation and why Robinson allegedly resisted arrest. "We don't know why he was doing it," Holloway said.

Robinson was the fourth person since April to die after struggling with police in Prince George's County.

On May 28, a Prince George's police officer fatally shot a Forestville man after he allegedly assaulted the officer, pinned her back to the hood of her patrol car and tried to take her gun in a residential neighborhood in Lanham.

Less than a week earlier, a Clinton man with a history of mental illness suffered a fatal heart attack as five officers tried to restrain him after he launched a series of karate kicks at a church van full of preachers.

On April 26, a 29-year-old carjacking suspect also suffered a fatal heart attack as he was shackled to a stretcher in a hospital emergency room shortly after he was chased and arrested by police near Andrews Air Force Base. Hospital officials said the man was resisting violently and had to be restrained by several people.

Yesterday's fatal shooting occurred in a stairwell directly outside Robinson's ground-floor apartment. Investigators and neighbors said that Robinson's wife and two sons--ages 2 years and 6 months--were inside the apartment but did not witness any part of the shooting.

William Hall, 27, a neighbor who heard the muffled sound of shots from inside his apartment, said Robinson was a friendly acquaintance who worked as a clerk at a Sports Authority store in Rockville. He said he was surprised that Robinson would get into an altercation with police.

"He's real cool and laid back, and I've never had any problem with him," Hall said. "I just can't see him carrying a knife and trying to pull it out on a cop."

Police said Robinson also went by the name Abdur-Raheem Muhammad. His relatives said yesterday that he had converted to Islam several years ago, but it was unclear if he changed his name legally.

The Honda that Robinson was driving is registered to Mohamed A. Khadar of Rockville, who confirmed yesterday that he is Robinson's father-in-law. Khadar said he had lent the Honda to his daughter but prohibited Robinson from driving it. Khadar said he and his wife were estranged from Robinson, although they remained close to their daughter and two grandchildren.

Researcher Bobbye Pratt contributed to this report.

CAPTION: Prince George's County police evidence technician W. Clelland, left, removes fingerprints from a police cruiser involved in the fatal shooting of a motorist in Laurel.