Turkey Vultures (not actually a buzzard if you are in the U.S.) will not attack living creatures unless starving. They do not have talons or beaks that are good offensive weapons. They also like really, really smelly stuff. So the normal defense behavior of an opossum, laying still in a death position and often emptying their bowels, triggered by the big birds being around, actually made them interested. All these animals seem a bit confused.
I used to do animal handling at a local zoo. We handled Turkey Vultures. They have a great defense: they shoot projectile vomit at the eyes of a perceived threat. Skunks got nothing on vulture vomit!!!