The San Diego County medical examiner said the remains found in Riverside County late Tuesday had been confirmed as those of Killgore, 22, of Fallbrook, who had disappeared Friday after telling friends she was going to San Diego's Gaslamp Quarter, ABC News reported. Her body was found about 20 miles from her home.
The San Diego District Attorney's Office said Jessica Lynn Lopez, 25, was being held on suspicion of first-degree murder in Killgore's death. Lopez had not yet been charged, office spokesman Steve Walker told ABC.
Lopez was transferred to the county jail from a hospital where she had been treated after being found with self-inflicted lacerations in a San Diego hotel Tuesday morning.
Investigators said they found an apparent suicide note in Lopez's room, in which she allegedly told what happened to Killgore and where her body was.
Authorities have not explained the relationship between the two women. Killgore had recently filed for divorce from her husband, a Marine deployed in Afghanistan.
Police have said they believe Louis Ray Perez, a 45-year-old Marine, may have been the last person to see Killgore alive. He was arrested Sunday on an unrelated weapons charge and remains jailed.
"Mr. Perez was not cooperative or what we felt was fully forthcoming in his interview," San Diego County Sheriff's Office Lt. Larry Nesbit told KABC-TV, Los Angeles. "He's being actively investigated for this murder."