SACRAMENTO (AP) – Authorities say a California prison guard has died five months after he and another officer were attacked by inmates.

The state Department of Corrections and Rehabilitation says Officer Armando Gallegos died at a hospital Sept. 14.

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The guards’ union believes his death is related to injuries from the assault, but the official cause is pending a coroner’s report.

The 56-year-old had worked in the state prison system for more than a dozen years.

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The two were attacked April 21 by a dozen inmates at Kern Valley State Prison in Delano.

Officials said then that one officer suffered injuries including broken vertebrae, swelling to his head and a concussion. The other officer suffered injuries to his knees, hand and face.

Prosecutors are weighing possible charges against the inmates involved.

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Copyright 2018 The Associated Press.