From the Atlantic [1]:
The SEALs' decision to fatally shoot bin Laden -- even though he didn't have a weapon - wasn't an accident. The administration had made clear to the military's clandestine Joint Special Operations Command that it wanted bin Laden dead, according to a senior U.S. official with knowledge of the discussions. A high-ranking military officer briefed on the assault said the SEALs knew their mission was not to take him alive.