A 65-year-old Baltimore police officer was shot and killed by another officer Thursday morning after he walked out of a bar with brass knuckles to join a fight outside, then drew a handgun after being hit with a Taser, police said.

Officer Norman Stamp was a 44-year veteran of the police department, making him one of its longest-serving officers, Police Commissioner Frederick H. Bealefeld III said at a news conference.

"Officer Stamp was a mentor to some and a friend to many," Bealefeld said. "This is an incredibly difficult time."

According to Bealefeld, uniformed officers responded shortly after midnight to reports of a fight outside the Haven Place Bar in southeast Baltimore. One officer stationed himself by a door to prevent anyone else from joining the melee, and that's when Stamp, who was off-duty, emerged wearing brass knuckles, Bealefeld said.

The officer fired his Taser at Stamp, who fell to the ground, then drew a handgun, Bealefeld said. The officer, "having no recourse, fired two shots from his departmental-issued weapon, striking Stamp at least one time," the commissioner said.

Stamp died at a trauma center around 1:30 a.m.

"This is a tragedy," Mayor Sheila Dixon said. "I did this morning speak with Officer Stamp's wife to assure her that we will be there with her and her family."

Stamp also leaves behind a daughter, said Paul M. Blair Jr., president of the city police union. He had served on the department's marine unit, which patrols the Inner Harbor, since the 1990s, said Sterling Clifford, a police spokesman.

The officer who shot Stamp did not recognize him, Bealefeld said.

Stamp is the seventh person shot and killed by Baltimore police this year, and there have been 10 police-involved shootings, Clifford said. Last year, officers shot 31 people, killing 13. In the past two months, two other police officers have been wounded by gunfire, and another officer was fired upon.

Police have attributed the recent gun battles with officers to the department's strategy of targeting repeat violent offenders with illegal guns.

The city has seen significant reductions in violent crime since Bealefeld became commissioner last summer. Baltimore is currently on pace for 185 homicides, which would be the lowest total in more than 20 years.