Jacksonville, N.C. ? Authorities said Friday they believe they found the shallow grave of a pregnant Marine in the back yard of a comrade she accused of rape, along with evidence inside his home that suggested she had been killed.

Investigators are treating the case as a homicide, said Onslow County Sheriff Ed Brown. But the prime suspect left a note insisting Lance Cpl. Maria Frances Lauterbach had killed herself, Brown said.

After some slight digging in a fire pit discovered in the yard of Marine Cpl. Cesar Armando Laurean, detectives found what “appeared to be burnt human remains,” Onslow County District Attorney Dewey Hudson said Friday night.

“We think we have found what will (contain) the skeletal remains of Maria Lauterbach,” Hudson said. Authorities placed a tarp and two white tents over the area and planned to begin slowly scraping the earth with garden tools Saturday morning.

Lauterbach, 20, vanished three weeks ago, days after she talked to military prosecutors about a rape case against Laurean, who remains at large. Authorities said Friday that information from another woman, a former Marine, left them certain that she is dead.

Before fleeing Jacksonville on Friday, Laurean left a note that said Lauterbach had “come to his residence and cut her (own) throat,” Brown said.

But crime scene investigators found blood stains and obvious signs that a cleanup had taken place inside the home, Brown said late Friday.

“Evidence now is showing that what he claimed happened didn’t happen,” Brown said.

Authorities learned about the note from Laurean’s wife, a person familiar with the investigation told The Associated Press on condition of anonymity because the investigation is ongoing. In the note, the person said, Laurean wrote that he had nothing to do with Lauterbach’s suicide, but that he had buried her body.

Laurean’s wife, Christina, is “heartbroken,” said her mother, Debbie Sue Shifflet.

“I feel sorry for the other family,” Shifflet said. “It’s horrible what they’re going through. My heart goes out to them.”

Authorities on foot and all-terrain vehicles searched Laurean’s neighborhood near Camp Lejeune on Friday. Megan Melton, who lives nearby, said dozens of vultures had descended on the area in the past few weeks.

Although the outdoor search was suspended for the night, investigators from the State Bureau of Investigation moved indoors and began a search for blood and other evidence inside his one-story, brown brick ranch home.

The search continued late Friday for Laurean, a 21-year-old from Clark County, Nev., who had refused to meet with investigators and apparently left the area without telling his lawyers where he was going, the sheriff said.