Of course, the best way is to negotiate with all parties involved at one place. Certainly, some of the people must be angry so you should know how to deal with them. I suggest you don't fall into the argument yourself, avoid using "YOU" statements as they sound accusatory and try to understand everyone. An easy way to try to solve the problem and yet not be involved in a fight is not to fight back. Instead, ask questions. Remember that in conflicts, people need to be heard without evaluation. Listen to everyone calmly and then in the end, present what you think is best with a proper reasoning without accusing anyone.