A fourth inmate in the Alabama prison system has died after testing positive for the coronavirus.

Robert Stewart, 80, who was serving a life sentence at Staton Correctional Facility in Elmore County for a murder conviction in Baldwin County, died at a local hospital on Sunday, the Department of Corrections announced in a news release. Stewart, who had some “advanced chronic health conditions,” was transferred to the hospital on June 8 after showing symptoms of the virus, the department stated. He was tested for the virus and the test returned positive on June 10. Following those results, inmates housed in the Staton infirmary were tested for the virus and 13 tested positive. Those inmates are now in medical isolation.

Three other inmates, all with pre-existing conditions and ranging in age from 66 to 80, have died over the past two months after testing positive for the virus.

The first positive case of COVID-19 in the prison system, that of an employee, was reported March 19. Since then, 41 positive cases have surfaced in the inmate population and 20 of them are still active. One hundred twenty-two full-time or contract employees have tested positive, and 30 have been cleared to return to work.