Robert Hanssen, a former FBI agent who admitted spying for the Soviet Union and Russia in exchange for $1.4 million in cash and diamonds, died Monday morning in a federal prison in southern Colorado, officials said.
Hanssen, 79, was found unresponsive about 6:55 a.m. at the United State Penitentiary Florence ADMAX in Florence, according to a news release from the Federal Bureau of Prisons. Prison staff initiated life-saving measures and called EMS, before he was pronounced dead.
He is believed to have died of natural causes, The Associated Press reported. No official cause of death was released.
Hanssen, whom the FBI called the “most damaging spy” in its history, was arrested in 2001 and later pleaded guilty to 15 counts of espionage for selling highly classified national security information to Russians. He was sentenced to life in prison without parole.
He had been serving his sentence in Florence since July 17, 2002.