Killer dies after being held in solitary confinement longer than any other U.S. prisoner

An inmate at the "Supermax" prison in southern Colorado, who had been held in solitary confinement longer than any other federal prisoner, has died at the age of 67. Thomas Silverstein, who was held in solitary confinement for 35 years, was admitted to a suburban Denver hospital in February to undergo surgery and died in intensive care May 11.

He entered prison in 1978 on an armed robbery conviction and was later found guilty of killing two inmates and a prison guard. The Denver Post reports that with no federal death penalty in place at the time of the guard's slaying, the Bureau of Prisons instead put Silverstein in indefinite solitary confinement, where he remained until he was hospitalized.

He was moved to "Supermax" in Florence in 2005 and was housed in a soundproof cell.

In Supermax, Silverstein wrote letters, drew, crocheted, practiced yoga and meditated, CBS Denver reported.

"It's almost more humane to kill someone immediately than it is to intentionally bury a man alive," he wrote in a 2008 letter to a friend.

Accused drug kingpin Joaquin "El Chapo" Guzman is expected to join a roster of infamous inmates at "Supermax" in Colorado. Those inmates include Boston Marathon bomber Dzhokhar Tsarnaev, "shoe bomber" Richard Reid and "Unabomber" Ted Kaczynski.