OAKLAND -- Even though interim police Chief Sean Whent personally knew just a few of the 52 Oakland police officers killed in the line of duty between 1867 and 2009, it is the sacrifice they made he will never forget.

Speaking at Thursday's annual memorial service for the fallen officers, he wanted to make sure those in attendance would never forget them, either.

"We will remember our officers for their bravery, their dedication, their selflessness and their heroism," Whent told the almost 200 people present at the police headquarters event, including relatives of those killed, police officers, Mayor Jean Quan, Alameda County District Attorney Nancy O'Malley and others.

Standing in front of a marble wall etched with the names of the dead officers, Whent, an 18-year-veteran, said the officers killed were "our partners, colleagues and friends. They will always be remembered as true heroes. We have not and will not forget the sacrifice," they made. He promised the relatives present, "We will continue to honor their memory."

To the police officers present, ranging from the newest rookies to senior commanders, he said, "Let us carry on the honored legacy they have left us. Let us hope and pray that we never have to add another name to this wall."

O'Malley told the audience that the officers killed "did not die in vain" and are owed a debt because "they gave their lives so that (the city) could be safe." Of the police profession, O'Malley said, "we are thankful to those willing to to risk their lives," who "provide protection and safety for all of us."

The oldest former spouse present was 88-year-old Shirley Nielsen Spitoni of Santa Cruz, whose then-husband, motorcycle Officer Donald Nielsen, was killed March 22, 1951 in a crash. They were married less than five years.

She is grateful for the annual recognition of the officers, but the ceremony is still bittersweet. "It makes me sad," she said. "It brings back a lot of memories. He was a real sweetheart, a very loving man."

Emotions at the ceremony were high, and more than a few people dabbed at tearful eyes during the singing of "Stand By Me" and later, "What the World Needs Now," by the Better World Youth Chorus of Hayward, composed of girls 4 to 13. They received a standing ovation after the second song.