'Entourage' Movie -- Death on Set

Tragedy struck on the set of the "Entourage" movie today -- TMZ has learned, a crew member's dog got hit by a car and died.

Sources tell us, Tucker -- a 1-year-old Aussie Shepherd -- somehow escaped from a production trailer and darted onto busy Wilshire Blvd near downtown L.A.

We're told Tucker was immediately taken to a nearby vet, but it was too late. The dog passed away from his injuries. Tucker was surrounded by friends and family at the time of his death.