Two men died hours apart on Wednesday afternoon inside Sing Sing Correctional Facility, bringing the total of deaths behind bars to three since correction officers at more than two dozen New York State facilities went on strike earlier this month.

Anthony Douglas, 67, who was locked up for nearly 40 years on a murder conviction for killing drug dealer in Brooklyn, was found dead inside his cell at 4:25 p.m., according to Thomas Mailey, a spokesperson for the New York State Department of Corrections and Community Supervision.

Officials said Douglas appeared to have taken his own life but the cause of death is yet to be determined, according to multiple prison advocates.