Missing Mother's Body Discovered After 'Significant Amount of Blood' Was Found Inside Home

Castillo had been missing since Thursday, November 10th, when police responded to a 9-1-1 call to Castillo's apartment after her sister and roommate Emily Castillo found what police called "evidence of a struggle" inside. At the time, Simi Valley Police Department said "a significant amount of blood" was located in the home and Rachel's whereabouts were "unknown."

Her cell phone, car keys and vehicle were all still at the apartment.

On Sunday, authorities released a new update saying her remains had been found earlier in the day.

"Based on evidence at the scene, officers suspected that a crime involving serious injury occurred. Rachel was entered into the Missing Persons System, and the SVPD Detective Bureau responded to the scene and took over the investigation. Detectives have been working continuously since that time to locate Rachel and develop leads in the case," announced Simi Valley PD.

"This afternoon, Detectives located human remains of an adult female in a remote location within the Antelope Valley," they continued. "The Detectives, along with the Los Angeles County Medical Examiner’s Office identified the remains as Rachel Castillo."

Authorities said "the primary suspect in this case" is Zarbab Ali, Rachel's 25-year-old ex-husband. He was arrested at her parents' home "in connection to Rachel's homicide," added SVPD.

"This investigation has rapidly evolved over the past few days," police ciontinued. "This case is still under investigation and some details cannot be released due to legal and investigative reasons. The Simi Valley Police Department will release additional details related to this case when it is available."

Rachel's mother Robyn Castillo told ABC 7 she actually spoke with Ali over the weekend, calling it a "very normal" conversation.

"He had my grandchildren, I had texted him to ask how he was doing," she told the outlet. "He offered to video chat so I could see the boys. I got to see my grandsons and speak to them and he expressed his concern and I just told him we're doing everything we can ... he said he was very sorry and hoped that she was okay. It seemed like a very normal conversation."

"I really didn't expect it to turn out like this," she added, saying the her daughter and Ali had what ABC 7 called a "mostly amicable" relationship with "some difficulties."

Castillo and Ali shared two sons, ages 2 and 5. Per the LA Times, she initiated divorce proceedings earlier this year.