An man convicted of murdering a woman after breaking into her apartment as she slept was put to death Thursday evening in Alabama in the nation’s fourth execution using nitrogen gas.

Frazier is set to die by nitrogen gas for the murder of Pauline Brown in Birmingham, Alabama in 1991. Critics say the method amounts to torture.

An Alabama death row inmate who raped and murdered a woman in 1991 was executed this week using nitrogen gas, making him the fourth person in the U.S. to die by the controversial method.