Updated 9:31 p.m. Tuesday.
A body believed to be that of Brittany Killgore was found in Temecula, according to police officials.
A maintenance worker found the remains around 2:30 p.m. today about a mile west of Lake Skinner on the side of Borel Road, according to Lt. Larry Nesbit of the San Diego Sheriff's Department.
"A road worker who was mowing the shoulder of the road made the discovery," Nesbit said.
Law enforcement and a police helicopter swarmed the area, taking residents of the rural area by surprise.
"We just saw all these police cars and helicopters," said Bonnie Monier, whose home stands a few hundred feet away from the place the body was found. "I don't think anybody around here saw anything (before law enforcement arrived)."
Deputies talked to the worker shortly before the discovery and asked him to keep his eyes open. "The body was not readily visible from the roadway," Nesbit said.
He declined to release the suspected cause of death.
Killgore, 22, went missing on Friday evening from Fallbrook. She was believed to be with 45-year-old Camp Pendleton Marine Louis Ray Perez.
Perez was arrested on suspicion of stealing an AR-15 military-type assault rifle in an unrelated incident, according to the San Diego Sheriff's Department. He was held in lieu of $500,000 bail today.
Another woman, Jessica Lynn Lopez, 27, was arrested this morning at a motel on Rosecrans Street in San Diego for her suspected connection to the murder.
She was admitted to UCSD Medical Center due to self-inflicted injuries and was under guard today. She is expected to be booked on a murder charge upon her release from the Hillcrest hospital. Officials declined to discuss Lopez's alleged connection to the case.
Killgore is married to another Camp Pendleton Marine, Cory Killgore, who is deployed in Afghanistan, though he was informed of what was happening and is en route to the area, according to Nesbit. The woman filed for divorce last week, according to court records.
Investigators went to the area where the corpse was found "based on leads stemming from the arrest of Lopez," San Diego County Sheriff's Department Capt. Duncan Fraser said during a late-afternoon briefing. The captain told reporters he could release very limited information about the case before heading north to the spot where the dead woman turned up.
"I can't comment on the condition of the body that was found," he said. "We have not confirmed that the body ... is that of Brittany Killgore. ... The medical examiner will make that confirmation."
On Monday, search-and-rescue personnel combed open areas in the De Luz area, north of Fallbrook, in hopes of determining what had become of Killgore. It was unclear what led them to that spot, but they exhausted their lead and called off the search this morning, Nesbit said.
Perez had been "uncooperative and not completely forthcoming about his knowledge," according to Nesbit. The lieutenant would not comment on the nature of the missing woman's relationship with the serviceman.
Among the suspicious circumstances in the case was the fact that Killgore's cell phone was found by trolley security guards in the Gaslamp District of downtown San Diego, even though investigators do not believe she had gone there herself on the night she vanished, Nesbit said.
-- City News Service contributed to this report