Updated at 6:00 p.m.

A 57-year-old man was arrested Friday after authorities say he fatally choked a woman at a Southeast Portland mental health treatment facility in May while they both were patients there.

Multnomah County prosecutors allege in court documents that surveillance video shows Roger J. Jones twice go into the room of Huyen Cao on May 17, where he at some point strangled her off camera. He goes into her room once around 3:40 a.m., stays for 17 minutes, leaves and returns briefly about 10 minutes later, according to a probable cause affidavit.

Cao, 46, was later found unresponsive in her bed by care center employees and pronounced dead some time after. Her bed sheets had been pulled up to her neck, the affidavit said.

An autopsy the next day by the Oregon State Medical Examiner’s Office determined she died of asphyxia due to being choked by another person.

Police contacted Jones on Friday and showed him surveillance footage from the care facility. He admitted to choking Cao, the county district attorney’s office said, and he was arrested.

The affidavit said Jones admitted to going into Cao’s room while she was asleep, choking her and covering her with a blanket.

The facility where Cao was killed is identified in court documents as the Cameron Care Center on Southeast Powell Boulevard. It’s one of three Portland residential care facilities operated by the company, which offers treatment for adults with mental illness.

A worker who answered the phone at the Southeast Powell Boulevard center said the company declines comment on the killing. Cameron Care, Inc CEO Corey Cameron and CFO Geraldine Cameron did not immediately respond to requests for comment Monday.

The district attorney’s office and Portland police haven’t released any more details related to the killing, such as why Cao was targeted or what led to the delay in Jones’ arrest.

The district attorney’s office said it wouldn’t release anymore details in the case, citing an ongoing investigation. A Portland police spokesman said Monday that he didn’t immediately have any more information on the case.

Monday was the first time Cao’s death in May was acknowledged by a public agency. Jones remains held at the Multnomah County Detention Center on suspicion of murder.

-- Everton Bailey Jr.

ebailey@oregonian.com | 503-221-8343 |@EvertonBailey

Visit subscription.oregonlive.com/newsletters to get Oregonian/OregonLive journalism delivered to your email inbox.