As Eric Clapton's "Tears in Heaven" played on a loudspeaker, motorcycles led a black hearse and a lengthy funeral procession of law enforcement vehicles down a hill and into the parking lot of the Grove Community Church in Riverside for the funeral of slain Riverside police Officer Michael Crain.

Crain, an 11-year veteran of the Riverside Police Department, was shot before dawn Thursday. Police said ex-LAPD officer Christopher Dorner opened fire on Crain, 34, and his partner as they sat at a red light in Riverside in a marked patrol car.

Riverside Police Chief Sergio Diaz called the attack a "cowardly ambush."

PHOTOS: Funeral for Riverside police officer Michael Crain

Law enforcement "did everything they could do to bring this man to justice," Los Angeles Mayor Antonio Villaraigosa told KTLA-TV on Wednesday morning. "I see them run into danger again and again and again."

Crain's funeral procession passed beneath a large American flag hanging from the ladders of two Riverside firetrucks. About 50 people stood nearby, watching. Hundreds were expected to attend the funeral.

In the parking lot, officers from dozens of police agencies stood at attention as helicopters droned overhead. One pickup truck across the street had "R.I.P. Officer" written in white paint on its back window.

PHOTOS: Manhunt for ex-LAPD officer

Mary Ann Taylor, who lives down the street from the church, watched the police cars file past with lights flashing. So did her twin 4-year-old granddaughters, Saydee and Sophee Salcedo, and their dog, a yellow lab named Milee.

"Put your hands over your hearts," Taylor said to her granddaughters. "Show some respect for them."

The girls attend the church's preschool, which was closed Wednesday for the funeral. They understand why they are out of school, Taylor said.

FULL COVERAGE: Sweeping manhunt for ex-cop

"I think all of us feel the sadness of the last few days," Taylor said. People in the neighborhood have been babysitting for each other, she said, because many children have police parents who are working overtime this week.

Los Angeles County Sheriff's Deputy Lt. Mike Reynolds was one of hundreds of uniformed officers outside, waiting for the funeral. "Any time one of us is out there and meets a tragic end, it hits us all hard," Reynolds said. "We all feel the pain."

Everyone is aware that Crain's family feels the most pain, Reynolds said. He hopes the show of support from officers will help comfort them.