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 convicted with three other men for the brutal slaying and mutilation of 37-year-old Vicki Lynn Deblieux.

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.