The 24-year-old officer was off-duty with his girlfriend and her brothers on July 27 eating at a taco stand in the area of Avenue 26 and Artesian Street in Lincoln Heights when he was shot and killed after he saw people tagging a building and told them to stop, police said. He had been on the force just two years.
Suspected gang members were charged last week in Diaz's killing, facing multiple charges that make them eligible for the death penalty.
A rosary and visitation were held Sunday evening at Forest Lawn in Hollywood Hills.
Diaz's funeral service is set for Monday morning at the Cathedral of Our Lady of the Angels.