Obviously, but where is the head of the person playing the decapitated body? The torso looks much too short for it to be hidden under the clothes. And if the whole thing is an animatronic then that's a very good animatronic.
I said, And you replied, ? Anyway, I believe the beheaded is slouched down and what you believe is a short torso, is not their actual torso. I believe it is similar to this partially explained trick/illusion: