A convicted killer serving a life sentence for four Los Angeles County murders killed his wife during a conjugal visit at a Northern California prison, authorities said.

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David Brinson, 54, killed his wife, Stephanie Brinson, 62, in November at Mule Creek State Prison in Ione, the Amador County Sheriff’s Office said this week.

Brinson was sentenced in 1994 to four consecutive life terms without the possibility of parole for killing four men during a robbery at a Los Angeles apartment, according to the Los Angeles Times. He is currently incarcerated at the California Health Care Facility in Stockton.

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The California Department of Corrections and Rehabilitation said Brinson alerted officers around 2 a.m. on Nov. 13, reporting that his wife had passed out. Staff attempted lifesaving measures, but she was pronounced dead at 2:51 a.m.

Amador County District Attorney Todd Riebe confirmed that Stephanie Brinson was killed during a conjugal visit but said he had not yet received reports from the prison to determine whether charges would be filed.

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This story originally appeared in the Los Angeles Times.