NEW : `` It was cleaner than I expected . Witnesses said the execution was fast . Ronnie Lee Gardner executed by firing squad . Supreme Court earlier denied stay of execution appeal . Third person executed by firing squad in U.S. in 20 years .
NEW : Witnesses said the execution was fast . Ronnie Lee Gardner executed by firing squad . Supreme Court earlier denied stay of execution appeal . Third person executed by firing squad in U.S. in 20 years .