Stanton, Calif. ? As authorities searched for the man who snatched and murdered 5-year-old Samantha Runnion, the sheriff issued a warning to the suspect: “Don’t sleep, don’t eat, because we’re coming after you.”

Orange County Sheriff Mike Carona said Wednesday that Samantha, whose body had been dumped in a ravine 50 miles from her home, was likely the victim of a serial rapist and serial killer.

Officials said there was no prime suspect and warned parents in the area to tell their children to stay away from strangers. The killer intends to strike again, authorities said.

“The way the body was found, the fact it was not buried, not hidden and such, and how it was left is almost like a calling card, like a challenge: ‘I’m here and I’m coming back again,'” Carona said.

An autopsy confirmed that Samantha was sexually assaulted and died of asphyxiation, Carona said. She had been alive for several hours after being abducted Monday evening, he said.

Samantha’s body was discovered Tuesday afternoon, less than 24 hours after she was abducted outside her apartment building while playing a board game with a friend. She was nabbed by a man who pulled up in a light green Honda or Acura and asked for help finding his puppy.

The Sheriff’s Department released a sketch and description of the kidnapper based on the account of a 5-year-old playmate who was with Samantha when she was kidnapped.

FBI agent Richard Garcia said the girl was able to identify speech patterns, and as a result, investigators believe the man is a Hispanic American. He was described as having slicked-back black hair and a thin black mustache. He wore a powder blue button-down shirt.

The sheriff said the killer may bear physical signs of a struggle. “He will probably have unexplained injuries to his hands, arms and possibly face,” said Carona.

Garcia and Carona each addressed the unknown killer directly during a televised news conference.

“We will find you and we will bring you to justice,” Garcia said.

“Don’t sleep, don’t eat, because we’re coming after you,” Carona said.

Samantha’s grandmother identified the girl’s remains through photos from the site where the body was found. The girl’s mother remained in seclusion after the body’s identification.

“Because the body was found very quickly, we have a high expectation that there will be significant forensic evidence found at the scene and significant forensic evidence found on the body of Samantha Runnion,” the sheriff said.

The White House called to offer any FBI assistance in finding the killer.

The abduction and killing follows the high-profile cases of 14-year-old Elizabeth Smart in Salt Lake City and 7-year-old Danielle van Dam and 2-year-old Jahi Turner in San Diego. Danielle’ body was found and a neighbor is on trial. Elizabeth and Jahi remain missing.

Brenda van Dam, Danielle’s mother, said she spoke with Samantha’s mother to offer consolation. “They were both sweet, wonderful girls who loved life and their family,” van Dam said in a statement.

The news of the abduction and murder spread fear in Stanton, a city of 38,000 southeast of Los Angeles.

Melissa Apodaca, 30, of Anaheim, brought her three children to Stanton on Wednesday to view a memorial for Samantha. She said she had made them watch newscasts about the abduction.

“They need to know this,” she said.

Samantha’s mother, Erin Runnion, and stepfather, Ken Donnelly, were at work and her grandmother, Virginia Runnion, was at home at the time of the kidnapping.

Samantha’s family said they moved from nearby Garden Grove to Stanton a year ago because they wanted a safer place for their three children where they could play outside without fear.