District of Columbia police circulated sketchy descriptions of four young men and a lookout for a late-model car yesterday as they pressed the search for the killers of a policeman in a Georgia Avenue go-go club Thursday night.

The four men were last seen speeding east on Decatur Street about 8 p.m. Thursday in a 1974 or 1975 Dodge or Plymouth, tan or beige, with a missing left hubcap, police said.

Moments earlier they had fatally shot Officer Bernis Carr Jr. as he and four employes lay on the floor of the club during a holdup.

Chief Burtell Jefferson, in a statement to the press yesterday, called the slaying "brutal and senseless," one that has "shocked" the police force and the community. He expressed confidence that the slayers would be apprehended "and dealt with severely by the courts."

Investigators disclosed yesterday that Carr's .38-caliber police issue revolver had been fired twice while the off-duty officer was in the club. But police said they did not know whether the 34-year-old officer or one of the bandits had fired the shots. One of the bullets from the gun was dug out of the club ceiling and police were searching for the other.

"Four shots were fired in the club, we know that," said Capt. Arif Mosrie, head of the homicide unit. The robbers fired two pistol shots into Carr's head and chest, apparently when they discovered that he was a policeman, police said. He died at Washington Hospital Center about an hour later.

Meanwhile police speculated yesterday that the same young men who shot Carr also may have held up a 14th Street bar the night before, and may have killed a man during a holdup in Northeast Washington on Feb. 9.

"These killers are still out there and if they are one and the same (as the suspects in the other incidents) they may well kill again," Morsrie said. He urged citizens with any information about the incidents to call investigators at 626-2727.

Homicide detectives worked double shifts last night and about 50 uniformed police combed the neighborhood around the club, Jimi's at 4801 Georgia Ave., in the search for clues.

Police still were having difficulty last night putting together the sequence of events leading to the officer's death, largely because the witnesses, who were themselves on the floor of the dimly lit club, gave contradicting and sketchy versions of what had happened.

As best as police could determine, the robbers entered the club at about 7:45 p.m. Thursday, announced a holdup and forced the occupants - a bartender, three go-go girls and Carr, who had been sitting at the bar - to lie on the floor of the club.

The robbers then searched each of the victims, taking about $100 from them. Before they could get to the cash register, police said, one of the gunmen apparently recognized Carr as a policeman.

Witnesses had reported that one of the robbers was frisking Carr and may have detected his service revolver, which off-duty officers are required to carry, or may have recognized his blue uniform tie, shirt and trousers, which he wore under a sports coat.

"Hey, man, I'm the police," Carr reportedly said as the robbers rolled him into his back. He also asked the intruders simply to take his money and not to kill him, according to some police accounts.

". . . you," one of the robbers reportedly shouted at the prostrate officer and began firing, according to several police sources. One bullt entered the right side of his head and the other struck the middle of his chest. Some of the witnesses were adamant that Carr never drew his service revolver, Mosrie said.

The robbers then fled, without taking time to rifle the cash register.

In a lookout bulletin issued yesterday afternoon, police describe the four as:

A black male, 17 to 22, 5 feet 4 to 5 feet 9, 130 to 150 pounds, slim build, wearing a green ski mask, a three-quarter-length dark color coat and brown pants.

A black male, 19 to 24, 5 feet 5, 140 to 160 pounds, dark complexion, small build, short dark hair, dark lether jacket and dark pants.

Two black males, small builds, 19 to 21, 5 feet 4 to 5 feet 7, both wearing dark clothing.

The getaway car, which police said resembled an unmarked police cruiser, may have been driven by a fifth man, police said.

Police believe the same men may have held up the Ebony Hut, a bar at 4726 14th St. NW at about 8 p.m. Wednesday. The four, some wearing ski masks, and one carrying a rifle or shotgun, burst into the club, forced the patrons and employees to lie on the floor, and fled with an undertermined amount of money.

On Feb. 9, three young black men, one carrying a sawed-off shotgun and two with handguns, entered a Chinese restaurant at 1601 Benning Rd. NE, announced a robbery, and within moments shot and killed an employee, Sze Cheng, when the victim apparently did not obey their commands. Cheng did not speak English. He was shot in the neck and died at the scene.

Carr was a 12-year veteran of the force who lived in District Heights, Md., with his wife, Dorothy, and their two children.

He had worked as a counselor for school safety patrols in the first police district, and was described by his susperiors as a "fine officer."

"Officer Carr had a great love for this city and a strong desire to help the youth of Washington grow up to become responsible adults and leaders in this community," Chief Jerrerson said yesterday.