A plainclothes D.C. policeman fatally shot a 29-year-old Northeast Washington man yesterday after the man attacked the officer's partner with a baseball bat, police officials reported.

The shooting victim, identified as Horace M. Swarn, of 1962 West Virginia Ave. NE, was taken by fire department ambulance to D.C. General Hospital, where he died about 90 minutes after the noon incident, according to police and a hospital spokeswoman.

Police said the officer who was attacked, David J. Lazorcak, 37, a 14-year veteran of the force, was treated at the Washington Hospital Center for severe bruises and released.

Officials said the incident occurred on Fenwick Street NE near West Virginia Avenue, where Lazorcak and another member of the D.C. police Repeat Offenders Project were seated in a parked, unmarked car. The Repeat Offenders Project monitors the activities of chronic criminals, frequently with undercover surveillance, but officials would not disclose why the officers were at that location yesterday.

Police sources said Swarn approached the officers' car "two or three times" and "harassed" them, then went to his home nearby and returned a short time later carrying a baseball bat.

Both officers were outside the car, police said, and Swarn began swinging the bat at Lazorcak, striking the officer several times.

Lazorcak's partner, identified as Charles A. Owens, 36, a 15-year veteran, then drew his service revolver, and ordered Swarn to drop the bat. When he ignored the command, Owens fired several shots, striking him in the abdomen, police said.

Owens, who is assigned to the 6th District and was on temporary assignment to the Repeat Offenders Project, was placed on routine administrative leave with pay pending a grand jury investigation of the incident.

A police source said the officers were in the area on "legitimate business" but refused to say if they were conducting any undercover surveillance. They said Swarn was not a target of any police surveillance.

One police source said Swarn may have known that the officers, both of whom were dressed in casual clothing, were in fact police officers.

One neighborhood resident who said she knew the victim complained that Owens may have acted too hastily in using his gun. "They didn't have to shoot him," said Emily Tyson. "He was a drug addict. Everybody knows what he is and what he does. The poor man was so twisted up it was pitiful."

Tyson and other neighbors said that within the last week police had come to the area to escort Swarn home after he was seen running naked in the street. A woman who identified herself as the mother of Swarn's 11-year-old son and 10-year-old daughter said that he was an occasional user of PCP.

Another resident of the area, a 15-year-old who did not wish to be identified, said Swarn frequently played baseball with neighborhood youngsters in a nearby lot. "He was out playing with us yesterday," the boy said. "He was usually the umpire."

At a news conference late yesterday, Assistant Police Chief Isaac Fulwood Jr. said that a police officer is justified in using his service revolver if he has reasonable grounds to believe a person is committing or attempting to commit a crime that may lead to the death or serious injury of the officer or innocent bystanders.

"It appears the officer was on sound ground in using his service revolver," Fulwood said. "One officer was struck with a baseball bat, which could have resulted in serious bodily injury . . . and his partner responded to his call for help."

Officials said that yesterday's incident was the first fatal shooting by police this year. There were seven last year, they said.