Bagpipers led the massive procession carrying Cottle's flag-draped coffin to the Roman Catholic cathedral. Cradling their 9-month-old daughter, Cottle's wife Emily followed behind, along with LAPD Chief Charlie Beck.
"R.J.'s passing will leave a hole that cannot be filled. It'll leave a scar on the hearts of not only peace officers but warriors that will never fully heal," said Beck.
Several streets in downtown L.A. were closed for hours to accommodate the funeral procession. Streets south of the 101 Freeway and north of 1st Street between Grand Avenue and Alameda Street were blocked off. Streets around the cathedral were also closed during the service, and bus service was interrupted by the morning funeral.
Friends and fellow LAPD say the 45-year-old SWAT officer and Marine was a true patriot, a loyal officer and a devoted father and husband.
"I never saw this man show any outward sign of fear of any task. What he would want us to remember is that he died doing what he loved being a Marine and serving his country. He would also want us to remember his family. Emily, in his last e-mail to me he said, 'I'm looking forward to getting back home to be with my wife and daughter. I miss them both immensely,'" said retired SWAT officer Dan Skinner.
"I had to be here to honor my friend and a hero. I looked up to Robert Cottle. I don't want to go on about how great he was, but he was everything they say he was," said retired LAPD officer Ulysses Taylor.
Dozens of people said a personal goodbye to the officer on Monday during a viewing at LAPD headquarters.
Cottle, of Yorba Linda, joined the LAPD in 1990 and began with SWAT six years later. Cottle is the first active LAPD officer to be killed in Afghanistan.
Cottle and Lance Cpl. Rick Centanni, 19, also of Yorba Linda, were traveling with other Marines in the Marja region of southern Afghanistan on March 24, when their armored vehicle hit an improvised explosive device, killing the two men and seriously wounding two other Marines.
During Tuesday's service, Cottle was posthumously awarded the Purple Heart and Bronze Star. At the end of the memorial, the LAPD issued an end-of-watch broadcast for "23-david," signing off the veteran officer for the last time.
"We will all miss you but our memories of you will live on forever. Rest in eternal peace my dear brother," said Cottle's sister, Bonnie Roybal.
Cottle is survived by his wife Emily, a naval officer, and their young daughter. Cottle is a veteran of two tours in Iraq and will be buried Friday at Arlington National Cemetery in Virginia.