Barry Mills, the brutal leader of the white supremacist prison gang called the Aryan Brotherhood, died on July 8 behind bars, where he had spent nearly three-quarters of his life, transforming himself from a teenage misfit to a charismatic national crime boss. He was 70.

His death, a day after his birthday, was confirmed by the Federal Bureau of Prisons. He had been serving four life terms at the maximum security penitentiary in Florence, Colo., where he was found dead in his cell. Randy Keller, the Fremont County coroner, said there was no evidence of foul play.

Bald, brawny and mustachioed, Mr. Mills sported sinister dark sunglasses (his eye had been injured in a prison brawl) and was known deferentially as the Baron.

But his avocation defied the stereotype of a vengeful killer: He enjoyed embroidering.

Mr. Mills was among 40 people indicted in 2002 for committing 32 murders, or trying to. They were charged under the Racketeer Influenced and Corrupt Organizations Act, typically invoked to prosecute organized-crime figures.