This past Saturday I held a party that was open to the public. I rented out a local bar and restaurant in San Francisco CA and under contract I was supposed to have security guards there. My security guards never showed up. Half an hour before the party was going to end. A fight broke out amongst three of the attendees. One of which was hit in the back of the head with a bottle and was injured. I am not sure however, of how badly. I am wondering what kind of rights do I have as the party thrower? Can those injured individuals sue me? What can I do to protect myself.