How do you discipline a 16 year old boy?

Our sixteen year old, who we are raising due to my husband's parents both ping away ( he's my hubby's little brother) did something very rude the other day. My neighbors who we have been trying to become freinds with in this new community we recently moved to were very offended by the Kevin. We had our window's open and Kevin shouted, very rudely, " Those neighbors are so loud and noisy! I hate them! I wish they would just shut up!" Now they heard every word of what he said, and I am mortified that they just asked me tonight when my 3 year old went to play with their 3 year old outside " do you think we are too noisy?" They looked hurt and upset. I am so angry at this sixteen year old little $(@9 that I don't know what to do. His behavior was horrible and now they think that our familiy doesn't like them; which is not true? What do I do? Make him go over there and apologize?