The execution is the 22nd in the U.S. this year and the sixth in Alabama, which has put three of the men to death using nitrogen gas.

Grayson was one of four teenagers convicted of capital murder in the torture, bludgeoning and mutilation of Vickie Lynn Deblieux on Feb. 21, 1994.

An Alabama prisoner convicted of the 1994 murder of a female hitchhiker became the third person executed by nitrogen gas in both the U.S. and Alabama.