Sierra Cuesta doesn't remember her dad.

But a group of officers do.

"We lost a brother out there and it hurts," said LAPD Sgt. Don Poirier. "Every day I look back and wish that something like this would have never happened."

Officer Fil Cuesta was shot in the back of the head as he waited for back up in his patrol car in the Crenshaw District.

That was 18 years ago.

His youngest daughter Sierra was just a month old. Her sister, a year old.

His fellow officers made a pledge they would be a constant presence in the girls' lives.

"We are kind of a father figure for them since Fil can't be here," said Poirier.

"To see everybody here, it's like he's here, he's here with us, you know," said Sylvia Cuesta, the girls' mother.

On Thursday, nearly 20 LAPD officers surprised their former partner's youngest daughter at her high school graduation in Yorba Linda.

"They're not just here for one thing, they've been here since I was growing up," said Sierra Cuesta. "It feels great!"

The officers did the same thing for Sierra's older sister last year.

"To see all of these men be here, and honor him, and love him, it speaks volumes to my children about their father," said Cuesta.

Sierra will be a lifeguard in Huntington Beach this summer. Then, she plans on attending a state university to study nursing.