Actress Angelina Jolie, who directed the 2014 film "Unbroken" based on the life of Louis Zamperini, former Olympic runner and World War II hero, says of his passing - "It is a loss impossible to describe".

Zamperini, whose life is the subject of Jolie-directed movie "Unbroken", died at the age of 97 from pneumonia Wednesday, reports aceshowbiz.com.

Jolie said in a statement: "It is a loss impossible to describe. We are all so grateful for how enriched our lives are for having known him. We will miss him terribly."

"Unbroken", whose script is based on Laura Hillenbrand's book "Unbroken: A World War II Story of Survival, Resilience and Redemption" on Zamperini's life, is set to be released Dec 25.