Former FBI agent Robert Hanssen was found dead in his cell on Monday. Hanssen, 79, had been arrested in 2001 and had pleaded guilty to selling highly classified material.
He was serving a life sentence at the federal penitentiary in Florence, Colorado. His revelations included details about U.S. nuclear war preparations and a secret wiretapping tunnel under the Soviet embassy in Washington, D.C. He also betrayed double agents, including Soviet General Dmitri Polyakov, who were later executed.