Police vehicles with flashing lights illuminated Interstate 80 en route to Vacaville Thursday morning. Firefighters on overpasses waved their support as the procession rolled by. An electronic road sign at the Leisure Town Road exit said a lot in a few words: "Our Hero. RIP. 18036."

The I.D. number belonged to California Highway Patrol Officer Kenyon Youngstrom, a seven-year member of the force who was fatally shot during a routine traffic stop on I-680 just nine days earlier.

There are few events more stirring or sorrowful than a memorial for a fallen law officer. So it was at The Mission Church, where profound respect and inexplicable grief took turns defining the day. Row upon row of uniformed officers -- from around the country and throughout the region -- filled an enormous chapel and overflow outside seating.

If this was an occasion for celebrating an honorably lived life, it was also a bonding of a brotherhood that understands how quickly a normal day can turn tragic in law enforcement.

CHP Commissioner Joe Farrow, speaking first, thanked all in attendance for being part of healing process that's needed after catastrophe. Then he added quietly that Youngstrom never was happier than in uniform.

"He truly loved and embraced the ideals associated with being with the California Highway Patrol," he said. "His dream was to become a CHP officer."

The message clearly resonated with an audience that moments earlier had stood at attention, shoulder to shoulder, saluting as Youngstrom's casket had been carried into the church.

Few groups band together like those in law enforcement. Perhaps that comes with the job. The successes and failures are equally shared, and one loss seems to affect all.

Theresa Becher, chief of CHP's Golden Gate Division and Youngstrom's boss, told the audience that she couldn't understand how her heart could be so broken and so full at the same time. She showered praise on first responders who raced to Youngstrom's aid when he was shot, from beat partner Tyler Carlton, to an Oakland firefighter who provided first aid, to police and Sheriff's deputies who expedited his trip to the hospital.

When family members spoke -- first Kenyon's brother Clinton, then his son Alexander -- they prefaced their remarks with deep thanks and appreciation for the support they had received from Youngstrom's colleagues in uniform.

The fond remembrances that emerged during the service -- Youngstrom's undying allegiance to the St. Louis Rams (running back Steven Jackson's framed jersey was on the dais), his conflicting loves of junk food and exercise, his living-room wrestling matches with his son -- were treasured like scrapbook memories by an extended family that on this day numbered more than 2,500.

Carlton, who served alongside Youngstrom on his final day in uniform, praised his partner's dependability and his upbeat attitude. He talked about how much his friend would be missed.

"Ken," he said, "I know you can hear me. I want to thank you from the bottom of my heart for always being there for me. I look forward to seeing you again, brother."

For the only time, the crowd rose to its feet and applauded. If you hadn't noticed before, you noticed then. Everyone in the room was family.

Contact Tom Barnidge at tbarnidge@bayareanewsgroup.com