SAN DIEGO -- A police officer fatally shot a man who advanced on him with a kitchen knife in hand at the North Park home he shared with his 85-year-old mother, authorities reported.

San Diego police went to the house in the 3400 block of Alabama Street shortly after 10:30 a.m. to evaluate the mental health of 55-year-old Bradford Sarten, who reportedly had been behaving in an aggressive and irrational manner, SDPD Lt. Kevin Rooney said.

When officers arrived, they were met outside the residence by Sarten's mother and sister, who told them he was "agitated" and had assaulted them, according to Rooney.

As they spoke with the women, the officers saw Sarten open and shut a door on the southeast corner of the home. They then walked into the house through the front door, announced their presence and directed him to show himself.

Moments later, Sarten walked out of the kitchen, holding a knife. When the officers ordered him to drop the utensil, Sarten refused, telling them "they would have to shoot him," the lieutenant said.

At that point, the man began walking toward the officers with the knife held out in front of him, prompting one of them to shoot him.

Medics took Sarten to Scripps Mercy Hospital, where he was pronounced dead about a half-hour later.

Police officials did not immediately release the name of the officer, a 10-year department veteran, who opened fire on Sarten.