Why is Hamas killing Palestinians?
First of all, what Hamas is doing is wrong. But they are acting in what they feel to be self defence. In 2006, the US was going to back a coup against the democratically elected government of Gaza, which resulted in Hamas attacking first, a sort of pre-emptive revenge attack. Unfortunately, they are still continuing and unoffical violence to members of Fatah is taking place. The same happens in the West bank by Fatah to members of Hamas, and of course in Israeli custody to both.