Constant Hitting and at a loss- what do you do that works?

I have a 2 yrs old constant hitter. Hits when he's happy, hits when he's angry. I have been consistent for MONTHS with time away from the group when he hits accompanied by a stern voice and "angry" face. I have no idea what to do because he hits anyways. He HATES when he has to go for time out, and cries, then 5 min later will do it again. His language IS limited, but he's bright and I know he knows better. He will literally walk up to someone reading a book and hit them in the face for absolutely no reason. I've had other hitters in the past, but they've all been very quick to learn that it's not ok.

What the heck do I do????

My son does this too. I just consantly am telling him not to hit and redirecting him when I see him about to hit someone. He knows exactly what he is doing too. I sometimes think he does it for attention.
If someone else has any ideas, I'd love to hear them too!

Do you think you could show him another option of physical contact rather than a hit? Do you think he is hitting because he wants their attention? or is he hitting because he wants your attention? when he does it, what kind of look is on his face? does he immediately look to you? maybe he just wants attention, and will take whatever he can get?
I would try 2 things:
1) I would give one day where "when he hits" ignore him...if a child comes to you and says "______ hit me", you look at the child (the one who got hit) and say "well, I guess we won't play with him right now!" have that child tell him, "you hit me and I'm not going to play with you now" walk away and play on the other side of the room. I would try my best to not let the "hitter" know I am watching. Have him feel completley ignored. (if he is doing it for attention, this may help him to stop, once you or anyone else gives him no acknowledgement toward his behavior, it may become less "thrilling to him)
2) Would also give a time to "redirect" the situation, IF you choose this option. you would have to pay close attention to ALL he does (not missing a single "hit"). When he hits a child immediately go to him and that child and "make him" do what is right...make him appoligize and then show him another option besides hitting. Have him rub that childs arm or pat the childs back gently, while the "hitter" is demonstrating "what is right to do" explain to him...."this is the way we touch our friends"
Those are the two ways I would attemp to handle it, along with communicating with the parents as well, sometimes children have older siblings who "hit" them....planting the seed! :) good luck