Can we sue the campground even though we have no leads on who actually hit my fiance?

My fiancé and his groomsmen were at an adult campground over the weekend. My fiancé saw a man trying to break into their cabin and as a result they got into a tussle when all of the sudden somebody came and hit my fiancé in the face a few times resulting in broken nose, fractured eye socket and lacerations on eye lids. The guys did not call the police for some odd reason but did contact camp security who did not call police or ambulance. Lots of medical bills coming our way and he is a wreck. Can we sue the campground even though we have no leads on who actually hit my fiance?