Highlander University

Duncan MacLeod has been beheaded. He is no more. He is singing [off-key] with the Choir Invisible. He has shuffled off his mortal coil. He's bought the farm. As a going concern, he is no longer operative. He sleeps with the fishes. He is at this moment bowling in the semi-finals of the Formerly Immortal Bowling League's Championship Series.

Whodunnit?