Jack Kevorkian, the U.S. doctor who was jailed for helping terminally ill people commit suicide, has died at the age of 83.

The former pathologist's attorney and friend says Kevorkian died early Friday at a hospital in Royal Oak, Michigan. He was hospitalized last month with kidney problems.

In 2007, Kevorkian was released from prison after serving eight years of a 10-to-25 year sentence for second-degree murder.

A jury in Michigan sentenced him in 1999 after a video aired on national television of Kevorkian administering lethal drugs to a patient suffering from the debilitating nervous system disease named after U.S. baseball player Lou Gehrig.

He had been jailed and charged in other cases for assisting suicides. His previous trials resulted in three acquittals and one mistrial.

Nicknamed “Dr Death,” Kevorkian said he helped some 130 terminally ill people end their lives, often allowing his patients to operate his so-called “suicide machine.”

Only a few U.S. states have legalized physician-assisted suicide. Oregon was the first to pass a law in 1997, while the state of Washington did the same more than 10 years later. A Montana Supreme Court ruling has effectively legalized the controversial practice in that state.