BOSTON — Cpl. Brian Oliveira was killed in battle during his second deployment to Iraq, the Department of Defense said, leaving behind a 6-week-old baby boy he had met only in pictures.

“Brian was the most dedicated and proud Marine I ever met,” said Heather Bostrom, 20, a former girlfriend who remained a close friend. “It was his life.”

The Pentagon said Oliveira, 22, died Monday from injuries suffered during fighting in Iraq’s Anbar province. No further details were available.

Oliveira was a squad leader assigned to 3rd Battalion, 1st Marine Regiment, 1st Marine Division, I Marine Expeditionary Force, based at Camp Pendleton, Calif. He left for his second tour of Iraq in May.

He joined the Marine Corps in January 2001 and received several medals, including the Combat Action Ribbon and the National Defense Service Medal.

Oliveira and his wife, who had made their home in San Diego, welcomed their son, Nathan, on Sept. 11. Oliveira originally was from Raynham

Oliveira’s parents, David Horseman and Lillian Oliveira, and a sister, Carolyn Horseman, all live in Fall River.