A sergeant at San Quentin State Prison died Sunday after a battle with COVID-19, marking the first virus death of an employee at the facility that has grappled with a large outbreak among both staff and inmates.

San Quentin has had 2,231 inmates and 261 employees test positive for the virus — the largest outbreak among California Department of Corrections and Rehabilitation’s prisons, which together have had 1,976 coronavirus cases among staff and 8,768 among inmates.

Twenty-four inmates have died of COVID-19 at San Quentin, accounting for nearly half of the COVID-19 inmate deaths at California state prisons.

Polanco is the ninth California state prison employee to die of COVID-19.

San Quentin had escaped a coronavirus outbreak until inmates from the California Institution for Men in Chino were transferred there in late May, when cases started to soar, the Associated Press reported.

As the coronavirus spread through the prison system, California officials in March started granting early release to prisoners who are serving terms for nonviolent crimes and are nearing the end of their sentences.