Scott McCloy of WorkSafeBC says the accident happened Monday night on the Burnaby, B.C., set of the TV series, "Falling Skies."
He says a five-ton truck was parked on a slope, with its tailgate down to unload equipment, when the vehicle rolled backwards and pinned the worker to a tree.
McCloy says the unidentified worker was taken to Royal Columbia Hospital in New Westminster, B.C., but died of his injuries.
Turner Entertainment Networks says in a statement it is saddened by the tragic event and expresses its condolences to the security guard's family.
"Falling Skies" tells the fictitious story about the aftermath of an alien attack on the world, and its executive production team includes Spielberg and other members of DreamWorks Television.
UPDATE: Amrik Singh Gill, 59, of Delta has been identified as the security guard who died during the film shoot. The BC Coroners Service, WorkSafeBC, and RCMP continue to investigate his death.
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