The Ominous Foreshadowing In Last Night's Episode

Glenn found a new weapon of choice in last night's episode of The Walking Dead. Noah led the team to a gated community in Virginia which had become a graveyard for its residents. 

The wooden bat Glenn found in the ruins, probably made most comic book readers pause. The infamous villain and raider, Negan, likes to use a very similar bat, and frankly, Noah's town doesn't look like it was just over-run by Walkers:



Who/What are the "Wolves" this graffiti is warning about?