Alan Eugene Miller, convicted of killing three men in separate workplace shootings in 1999, was executed in Alabama using nitrogen gas on Thursday.

Miller, 59, was the second person in the U.S. to be executed by this method, which causes death by depriving the body of oxygen.

He was pronounced dead at 6:38 p.m. after about six minutes of gasping breaths.

Miller, a delivery truck driver, killed his coworkers after accusing them of spreading rumors, Fox News has reported.

Alabama Gov. Kay Ivey stated that “justice was finally served” for the victims.

Written by B.C. Begley