Demetrius Frazier became the fourth inmate in the US to be put to death by the method as he served his sentence for the 1991 murder of Pauline Brown at the Holman Correctional Facility. Frazier, 52, was convicted of capital murder for breaking into Pauline Brown’s Birmingham apartment and raping her at gunpoint before killing her when he was 19.

Demetrius Terrance Frazier was the fourth person executed in the United States using nitrogen hypoxia, which involves replacing breathable air with pure nitrogen gas

The state has never used that method to execute a prisoner. The last time an inmate was killed by a firing squad was in 2010 in Utah.