Chicago mobster Joseph Lombardo, better known as “Joey the Clown,” died in prison Saturday at the age of 90 while serving a life sentence for murder, multiple media outlets reported citing federal prosecutors.

A cause was unclear, but the Chicago Tribune reported that he had suffered from throat cancer.

Lombardo was sentenced in 2009 for the murder of his friend Daniel Seifert, a federal witness, in 1974 while his wife and 4-year-old son were present. Investigators said Lombardo was responsible for the slaying by a group of masked men, but Lombardo denied responsibility.

“In the end, we are judged by our actions, not by our wit or smiles,” said U.S. District Judge James Zagel when he sentenced Lombardo. “In cases, like this, we are judged by the worst things we have done, and the worst things you have done are terrible.”

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Lombardo arranged for Seifert's murder after supposedly learning his friend planned to testify against him in federal court, the Chicago Sun-Times reported.

Lombardo supposedly earned his “Clown” nickname because of his jokey demeanor despite his cold-blooded nature. When he finally made it to court after his 2007 arrest, he reportedly said he'd been “unavailable.”

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Separately, he was sentenced to prison in the 1980s for conspiring to bribe a U.S. senator and his role in a scheme to skim $2 million from a casino in Las Vegas, the Tribune added. He reportedly started out as a driver for Chicago Outfit figures before rising through the ranks.

Lombardo’s death was announced in a court filing by Assistant U.S. Attorney Amarjeet Bhachu, the reports said. No further details about his death were provided.