I've had my dog Sam for four years. He was abused as a tiny pup, but the shelter got him at three months old (approx) and I got him at six months old. He's never shown any signs of aggression whatsoever. Out of the blue tonight, my son (17) was laying with him on the couch & Sam growled & lunged at his face. My son was fast enough to stop him before he got to him, but WOW!!! WTH?! I am dumbfounded and don't know what to do.