An off-duty Baltimore police officer was shot and killed early yesterday as he stepped outside a bar in apparent retaliation for testifying against two men convicted of wounding him during an ambush last year.

Detectives, who described the shooting as a "flat-out execution," arrested three men in the killing of Detective Thomas G. Newman, 37, and charged them with first-degree murder.

The death of the 12-year veteran sent waves of fear and anger throughout the city Police Department as officers tried to cope with the brazen attack on an officer who did nothing more than testify against those who had tried to kill him. It is the third incident in eight days in which city officers have been hit by gunfire; five were wounded.

"This has been a really rough stretch for us," Mayor Martin O'Malley said. "This is a horrible loss for the city."

Speaking at a news conference yesterday afternoon, Baltimore Police Commissioner Edward T. Norris said detectives were "strongly" looking at the link between Newman's death and the previous attack.

Norris declined to discuss specifics of the shooting.

But police said one of the three men in custody was the half-brother of Andre A. Travers, 25, who was convicted of attempted second-degree murder in the near-fatal shooting of Newman in April last year.

Police identified Travers' half-brother as Raymond Saunders, 22, whose last known address was in the 800 block of Fifth Ave. in Halethorpe.

Police sources could not say what role Saunders played in yesterday's shooting. They identified the other two suspects as Jovan J. House, 21, of the 2000 block of Dorton Court and Anthony A. Brown, 34, of the 1000 block of N. Chappel St. All three have been charged with first-degree murder and were being held at the Central Booking and Intake Center last night.

Saunders' other half-brother, Larry Travers, 27, said last night that Saunders has been accused of a crime he did not commit. "That just doesn't sound like my brother," Larry Travers said. "He doesn't have that type of mentality."

Saunders, Brown and House have been convicted of minor drug offenses, court records show. It does not appear that they had been charged with any violent crimes before yesterday's shooting.

Police sources said that Saunders spotted Newman in Joe's Tavern in the 1000 block of Dundalk Ave. in Southeast Baltimore - one of the officer's favorite hangouts. Saunders then went to find friends, police sources said.

As Newman left the bar with a girlfriend about 1:50 a.m., two men approached him and opened fire without uttering a word, police said.

Newman fell to the ground, police said, and the gunmen stood over his body, aimed and continued to shoot.

Three bullets struck the officer's chest, and at least one was found lodged in his heart, Norris said. The girlfriend was not injured, and police declined to provide more details.

Norris, who had visited Newman in the hospital after the officer was wounded last year, said he was allowed to see Newman's body early yesterday.

"That confirmed my worst fears," Norris said. "This is awful. It looked like he had been executed."

After yesterday's shooting, the two men jumped into a waiting car and sped away, police said. A man working as a security guard near the bar watched the shooting, grabbed the officer's gun, jumped into a car and followed the three men, police said.

The security guard fired at the men during the chase but did not hit anyone, police said.

As the fleeing men entered the O'Donnell Heights housing complex, police said, they spotted the security guard, jumped out of their car and scattered.

One of the men was found cowering in a shed, and investigators tracked down the other two men by mid-morning, according to detectives.

Police recovered a 9 mm handgun and a .32-caliber handgun, both used in the shooting of Newman, and obtained tape-recorded statements from the suspects.

"There is no doubt they knew what they were going to do," said one police source close to the investigation. "We have a clear indication that they knew he was a police officer. They knew he was the police officer involved in the other incident."

Gary McLhinney, president of the Fraternal Order of Police Lodge 3, said prosecutors should seek the death penalty because Newman's killing was clearly linked to his law enforcement duties.

"There is no wiggle room here," McLhinney said. "He was killed because he was a cop, and these scum deserve the death penalty."

A spokeswoman for State's Attorney Patricia C. Jessamy said yesterday afternoon that her office could not comment on death penalty deliberations because charges had not been filed at that time.

The shooting was eerily similar to the one Newman barely survived on a dark street in April last year.

About 2:30 a.m. April 21, Newman was off duty and driving south on Baltimore-Washington Parkway when he pulled off to get gasoline and sodas at an Amoco station at Cherry Hill Road and Waterview Avenue.

As he got out of his car, several men began taunting him, and an argument broke out. During the confrontation, one of the men hinted that he had a handgun. Newman told the men that he was a police officer and that he also had a weapon.

The argument seemed to peter out, so Newman went inside the station to buy sodas. But one of the men entered the store and told the off-duty officer that he had guns and knew where to find him.

The incident shook Newman,As he was trying to leave, the men taunted him again from across the street before driving away in a Mazda MPV.

As Newman left the parking lot, he spotted the van. Worried that the men might be dangerous, he called 911 dispatchers to ask for backup and began following the Mazda.

He spotted it about parked at Salerno Place near Norfolk Avenue in the Westport community. Newman had no idea that two men had slipped away from the van and were waiting for him.

A few hundred feet from the Mazda, Newman stopped and was talking to 911 dispatchers when shots rang out. The two men had silently approached Newman, who was hit twice in the back of the neck but managed to scramble out of his car and fire one shot that missed his attackers.

Police said at the time that as many as five men were involved in the shooting, but they were able to identify only two - Travers and Marcellus Henriques, 22. Both were convicted in March of attempted second-degree murder and were sentenced three months later to 30 years in prison.

"He still had the bullets in him" when he testified this year, said Ahmet Hisim, an assistant state's attorney who prosecuted the case. "He was in pain."

After the shooting, Newman impressed many of his colleagues by overcoming his injuries and returning to work.

He was a member of the Warrant Apprehension Task Force, a demanding unit that requires detectives to hunt for dangerous suspects accused of violent crimes. But he did not let the physical labor deter him from returning to the job, said Maj. George Klein, the unit's commander.

"He was a hard worker and conscientious," Klein said. "He almost died the first time he was shot, and he survived it and had a rough recovery. He pushed himself to come back."

The physical and emotional toll of the shooting and his long recovery pushed Newman to seek a less demanding job. He transferred to a small unit that specializes in fraud investigation.

Newman, who lived in Baltimore and has family in Prince George's County, was a frequent customer at Joe's Tavern for about four years. Sometimes, he even acted as a security guard.

Patrons and workers described him as a friendly guy willing to help a friend or offer advice.

"You couldn't find a better person," said Tom Townsend, 59, who runs the package goods section of the bar. "He never drank very much, and he liked to smoke a cigar now and then. I'm telling you, he was a prince."

Newman is survived by a 6-year-old son and a 3-year-old daughter.