A group of people at a 4th of july celebration, with one man standing on a stage with american flag colored decorations around him.
A group are celebrating the 4th of July.
If they are at a celebration, they are celebrating.
standing on a stage with american flag colored decorations around him is inferred as  celebrating.
You would assume that a group of people at a 4th of July celebration are in fact celebrating the 4th of July.