Tough Guy

My son is almost 14 months old. He is totally adorable and he is my entire world. Though, we have been having some issues with him. He hits! I don't just mean the occasional love tap. Whenever he has access to a face, he smacks it. His cousin, who lives with us also, is 9 months old. My son attacks him daily. He will punch the top of his head or push him down when he is trying to sit up. I have had friends over who have babies and he does the same thing. I like to think that he doesn't realize what he is doing, but as he is getting older that theory is becoming less likely. I sternly tell him no and remove him from the situation. I have tried showing him how to gently touch someone, but as soon as I free him, he is off to attack again. Is anyone else experiencing something similar with their child? What do you do? Is this just a phase? Or do I have a future assassin on my hands??