The remains of a missing California mom have been found and her ex-husband has been deemed a primary suspect, The Simi Valley Police Department says.

25-year-old Rachel Castillo was reported missing on Thursday, Nov. 10, when her sister, Emily, returned home to find a large amount of blood and evidence of a struggle at the apartment they shared together, according to a news release from the department. 

The Simi Valley Police Department says Castillo’s phone, car keys and vehicle were found at the residence. Based on the evidence, they suspected a crime involving serious injury and entered Castillo into a database of missing persons cases. 

Later that day, investigators found the remains of an adult woman in Antelope Valley, a remote area north of Los Angeles and near the Mojave Desert. They identified the remains as Castillo. 

A missing sign shows Rachel Castillo, whose remains were found on Nov. 10.

CBS Los Angeles

The police department says Castillo’s ex-husband, Zarbab Ali, was arrested at his parents’ home in nearby Victorville, in connection to the homicide. He is a primary suspect. 

“This investigation has rapidly evolved over the past few days,” the department said in a press release. “This case is still under investigation and some details cannot be released due to legal and investigative reasons.” Further details will be provided when available.

Castillo was a single mother, according to CBS Los Angeles. She and Ali had a 5-year-old and 2-year-old together, according Castillo’s family, who said that Ali would pick up the children every Thursday morning.