More details on a story briefly covered earlier-

[Specialist Sean Baker] was to wear an orange prison jumpsuit while he played the role of an uncooperative detainee during a training exercise. A five-man response team of MPs came into the cell to subdue him, not realizing that he was a U.S. soldier. They were told only that he had been pepper-sprayed after having attacked a sergeant.

He was quickly knocked down, choked and pounded into the ground. Despite giving the code word and desperately telling the MPs, “I’m a U.S. soldier! I’m a U.S. soldier!” he was not able to stop the beating.

The physical assault halted only when the prison jumpsuit was accidentally pulled down during the scuffle, revealing Baker’s military uniform.

An investigation in February 2003 determined that a criminal inquiry was not warranted. None of the soldiers involved have been disciplined. Military spokespeople said that while the injuries Baker received were “unfortunate,” they were necessary since the United States likes its soldiers to undergo training that is “as realistic as possible.”

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I’m thinking I’ll never fully understand how something like this can happen.