A release from the city mayor's office said Hickenlooper appeared to have died of natural causes. City police will conduct an investigation, though foul play is not suspected, The Denver Post reported.

Hickenlooper's cousin, Denver Mayor John Hickenlooper, said the family was "devastated," the Post said.

"Shock and sadness do not begin to describe our emotions," the mayor said in a statement.

"George had immense creative talents and cinematic gifts, but he was so much more than that to us and all his family. His passion for life, zeal for people and unquenchable curiosity enriched everyone who had the fortune to know him. We will miss his sense of humor, his warm character and the avid encouragement he gave anyone around him. Our hearts go out to his wife, Suzanne, and his son, Charles."

"Casino Jack," starring Kevin Spacey as Washington lobbyist Jack Abramoff, is to debut at the Starz Denver Film Festival Thursday night.

Festival Director Britta Erickson said the festival will be dedicated to Hickenlooper.

"This is a terrible loss. He was a great, great friend to us and our hearts go out to his friends and family," she said.

Hickenlooper's credits include 1991's "Hearts of Darkness: A Filmmakers Apocalypse," about the making of "Apocalypse Now," and 2003's "The Mayor of Sunset Strip."

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