(NewsNation) — The ex-husband of a missing California woman has been arrested after investigators say her remains were located within the Antelope Valley.

Rachel Castillo, 25, of Simi Valley, was reported missing Thursday evening by her sister. Emily Castillo told police she found evidence of a struggle inside her Wood Ranch-area apartment that she shares with her sister when she got home that night.

Emily could not find her sister even though her personal belongings, such as her cellphone, car keys and vehicle, were still at the apartment.

Based on the scene, Simi Valley Police determined that a crime involving serious injury occurred. In a missing persons alert, police said a “significant amount of blood” was found in the apartment.

As detectives continued to develop leads in the case, they discovered the remains of a woman Sunday afternoon in a remote location in the Antelope Valley. The Los Angeles County Medical Examiner’s Office identified the remains as Rachel Castillo.

Simi Valley Police identified Rachel’s ex-husband, 25-year-old Zarbab Ali, as the primary suspect in the case and arrested him Sunday at his parents’ home in Victorville in connection to the homicide.

“This investigation has rapidly evolved over the past few days. This case is still under investigation and some details cannot be released due to legal and investigative reasons,” Simi Valley Commander Ritchie Lew said in a news release.

NewsNation affiliate KTLA reports that Ali and Castillo have two young sons, a 5-year-old and a 2-year-old together.