SIMI VALLEY, Calif. (AP) — Police said they found the body of a 25-year-old mother of two who disappeared from her Southern California home last week, and her ex-husband was arrested as the primary suspect.

Rachel Castillo disappeared Thursday, and relatives reported they discovered blood at her Simi Valley apartment, where she had left behind her phone, keys and car, police said.

“Based on evidence at the scene, officers suspected that a crime involving serious injury occurred,” the Simi Valley Police Department said in a news release.

The young woman’s body was found Sunday afternoon in a remote area of the Antelope Valley in the desert of northern Los Angeles County, police said.

Castillo’s ex-husband, 25-year-old Hawthorne resident Zarbab Ali, was arrested later Sunday at his parents’ home in Victorville, police said.

It wasn’t known Monday if Ali has an attorney who could speak on his behalf. He was held in lieu of $510,000 bail on suspicion of murder and was scheduled to make his first court appearance Tuesday, according to Ventura County inmate records.

“This investigation has rapidly evolved over the past few days,” police said in Sunday’s statement. “This case is still under investigation and some details cannot be released due to legal and investigative reasons.”

Rachel Castillo was last seen by her sister, Emily, Thursday morning at the apartment where they lived with Castillo’s two sons, ages 2 and 5.

Castillo was studying for a master’s degree in clinical psychology at Pepperdine University’s online program with plans to become a marriage and family therapist, according to the Los Angeles Times.