i dont think shanes all that psycho.....
mind you he has a very quick temper and speaks his mind but push comes to shove he has proven himself to be very reliable when it comes to protecting the group.
before rick showed up shane was calling the shots and the group was big and happy. it really wasnt till rick got there that SHTF. mind you yes this is a show and it would have made for a very boring show to watch people live in a old quarry but still
i think shane is just fed up with the fact that they have a place that compared to where they have been is safe and they have the means to survive. i think he is also dealing with the tension between lori and him and also his best friend being back. what he did to otis was wrong and sad but he really did do it for the better of the group. everyone knows that otis would have slowed shane down and gotten him killed. if shane cared about self preservation i think he would have just dumped all the medical gear and taken off. instead he had carl on his mind and did what he had to do.
all in all the show to me is really doing a great job of showing MANY MANY angles of what life would be like for a group of survivors after a zombie invasion. this show is really evolving and the writers and actors are doing a great job. cant wait till feb!!!