Robert, 50, was put to death at 10:24 p.m. moments after saying his final words, "It is done," KSFY-TV, Sioux Falls, reported.
Robert and accomplice Rodney Berget were convicted of killing Corrections Officer Ronald "RJ" Johnson during an escape attempt at the South Dakota State Penitentiary on April 12, 2011. He had been serving an 80-year sentence for kidnapping at the time.
He chose to fast in the 40 hours before his execution, consuming his last meal -- Moose Tracks ice cream -- Saturday, his attorney, Mark Kadi, said.
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