Could be. We've had problems with large stray dogs breeding with coyotes, they're called "coy-dogs". They travel in packs and can be extremely vicious. A while back there were some children picking blackberries not even far from their house and were attacked by a pack of coy-dogs. The kids had their lab with them and their dog fought off the coy-dogs. The lab suffered some injuries but was okay and probably saved those kids. Plus, their mom came running with a shotgun.
Lucky kids.The lab deserves a medal.Canines of any breed can be especially agressive when in a pack.I spent a few months in upstate(rural)NY,and my uncle said packs of domestic dogs will chase down full grown deer in winter.Solution-shoot on sight.
I have seen some coy-dogs as large as German Shepard, they just stand and look at you, don't run like a coyote will.