The word I heard was that bin Laden was found in an upstairs room. There was a woman with him (not necessarily "in flagrante delicto"). He was told to surrender and come quietly. He grabbed the woman to use her as a shield and was reaching for a weapon when the raiders opened fire, trying carefully to avoid wounding the woman and hitting him twice in the head.

That was the report that I heard. Your mileage may vary.

Don Firth