The body was found by a road worker off Warren Road near Lake Skinner in Riverside County at about 1:30 p.m., San Diego sheriff's Capt. Duncan Fraser said in a news conference.
Brittany Killgore, 22, went missing on Friday, just days after filing for divorce from her husband Lance Cpl. Cory Killgore, a Camp Pendleton Marine stationed in Afghanistan. Police say her cellphone was found at San Diego's Gaslamp District, but it was unclear whether she was actually there.
Authorities say they were led to the body from a suicide note left by 25-year-old Jessica Lynn Lopez. The note detailed the murder and the location of the body.
Lopez was arrested at a Ramada Inn in San Diego on suspicion of murder. Investigators say they found her with several cuts in an apparent suicide attempt. She is currently in a San Diego hospital under guard. It was unclear what her relation was to Brittany Killgore.
Another Camp Pendleton Marine, 45-year-old Luis Perez, was also arrested on an unrelated charge of being in possession of a stolen military assault rifle. Detectives believe he was the last person to see Brittany Killgore.
"Mr. Perez was not cooperative or what we felt was fully forthcoming in his interview," Lt. Larry Nesbit of the San Diego Sheriff's Office said. "He's being actively investigated for this murder."
Cory Killgore is returning home on emergency leave because of the investigation. Officials say he is not considered a suspect in the case.
Dozens of deputies searched the remote De Luz Canyon outside Fallbrook. The area is only a few miles from Brittany Killgore's apartment.
Simeon Pagdilao, also a U.S. Marine, served in Afghanistan with Cory Killgore.
"She's just been doing her own thing and telling everybody she's getting a divorce," he said.
Pagdilao said he told Cory Killgore about the divorce.
"He seemed upset but determined to fix it," he said.