SAN DIEGO -- An investigation is under way Tuesday into the killing by police of a man who allegedly stole a steak knife from a restaurant and used it to try to rob another eatery before raising the weapon at an officer.

The man, identified as Phillip Sewer, was killed by a 7-year San Diego Police Department veteran at Fourth Avenue and E Street in the Gaslamp District, said police Lt. William Stetson.

Police received a report at 4:23 p.m. Monday that a man believed to be a transient had just stolen a steak knife with a five-inch blade from a patio table at Greystone the Steakhouse in the 600 block of Fifth Avenue.

Sewer threatened Greystone employees when they confronted him, then walked away, Stetson said.

He then walked into another restaurant in the 800 block of Fourth Avenue, brandished the knife and demanded money, Stetson said, adding that he left when a restaurant employee did not acknowledge the threat.

Minutes later, a police officer approached Sewer a few blocks away at E Street and Fourth Avenue and ordered him to drop the knife, Stetson said.

"The suspect refused and instead advanced on the officer in a menacing manner while screaming obscenities with the knife raised," the lieutenant said. "The officer fired his handgun at the suspect. The suspect was pronounced dead at the scene."

Sewer turned 48 last month, according to county coroner officials.

10News learned Sewer may have been suffering from a mental illness.