Are the bones light and perhaps hollow That may lend creedence to the bird theory, Witha femur of approx 7 inches I'm gonna shay away from the deer/mnt lion theory I don't know your area, but I am often shocked by the kinds of wildlife that can be found in unlikely places, We have had a couple of coyotes running around in the heart of NYC periodically for the past few years, Also Large owls like ones that inhabit the pacific Northwest are quite capable of taking pretty big animals and can often hunt in relatively suburban areas without detection so that might be a likely assasin as for the target, Without a skull or feathers or skin it's hard to say? Large bird, Fox< or some domesticated animal would be my guess