ONTARIO, Calif. (AP) — Authorities in Southern California say a retired Army captain missing for a month is now presumed dead and her ex-husband has been arrested on suspicion of murder.

Police in the city of Ontario say forensic evidence in Julia Jacobson's abandoned SUV led detectives to believe she was killed. Investigators declined to elaborate and did not disclose a motive. No remains have been found.

Dalen Larry Ware was taken into custody at his home in Phoenix Friday. He'll be transferred to California to face a murder charge. It wasn't immediately known if Ware has an attorney.

Jacobson was last seen Sept. 2 and days later her SUV was found near her San Diego home with keys in the ignition.

An Army veteran, the 37-year-old Jacobson served two tours in Iraq.