FAIRFIELD, CA - Police said a 13-year-old girl reported missing Thursday has been found dead in a park in the Northern California city of Fairfield.

Fairfield police Officer Cleo Mayoral said passer-by Eric May discovered the girl's naked body a little before 7 a.m. Friday in the city's Alan Witt Park.

"The first thing I did is I yelled at her; I yelled at her, 'Wake up! What are you doing there? Wake Up!'" May explained. "No response, and then I reached down and I touched her. She's cold, cold! I knew there was no life left there."

Mayoral said the girl was reported missing around 5:45 p.m. Thursday after she had left a foster home in nearby Suisun City. Her name hasn't been released.

Fairfield Police Sgt. Rob Lenke explained the department remains vigilant.

"We're all parents, we all have families. Any time you are working with a young child, especially 13 years old, it definitely heightens everybody," Lenke said.

On Saturday, friends of the girl laid flowers and candles in a memorial to honor her life.

"That 13-year-old girl was my friend," Kayla Silva said.

Silva said the girl was a foster child and a 7 th grader at Green Valley Middle School. She said she loved to sing.

"We practiced singing. We used to hang out. Talk about girl stuff, drama, friends. You know, girl stuff," Silva said.

Even those who didn't know the girl were affected by the news and visited the teen's memorial.

"[I came] to show her that we cared about her and she's just not a lost soul. She's someone that mattered," Olivia Griffin said.

May is hoping the killer has a guilty conscience.

"Please turn yourself in, please."

An autopsy was performed, but Lenke said officials aren't releasing the results; he did say that when the girl's body was found there were no obvious signs of trauma.

No suspect information has been released, but Mayoral said detectives were canvassing neighborhoods and checking video images from surveillance cameras as part of their investigation.