This year's turnout was the biggest ever.
About 100 family members walked in a procession from the police union offices to the police department. The service is held every year to honor the officers who died in the line of duty.
51 Oakland officers have lost their lives since 1867. Their names are etched on a wall. For each one, a white rose was placed in a floral arrangement resembling a police star.
Officer Thomas Prindiville was killed in a motorcycle accident in 1941. His niece Pat Parson attached a rose for him.
"I just keep up the family tradition. I've been coming since it started 13 years ago," she said.
This year is different.
Four officers were killed in one incident in March. Their names were just added to the wall. They were shot to death by 26-year-old /*Lovelle Mixon*/. Police said this week DNA analysis revealed that on the day of those murders Mixon raped two women at gunpoint.
"It's very disheartening to know that he did all this stuff and then on that day he decided to take on and kill four of our officers," said acting Oakland Police Chief Howard Jordan.
On Wednesday their family members placed white roses on the memorial arrangement for Sgt. Mark Dunakin, Sgt. Ervin Romans, Sgt. Daniel Sakai and Officer John Hege.
"He was a good officer who wanted to be a motorcycle officer and did what he wanted to," said Hege's mother Tamra.
"May the work we do to bring peace to the streets of Oakland stand as a living witness to the courage and dedication we remember today," said Father Jayson Landeza during the ceremony.