Murder in a box

A man was murdered in a black box. Under every conditions there is no possibilities of entering the box. Within the box is an empty space established by the box shape where only the body of the man lied in the middle, while there is nothing else. It is impossible to be inside the box for every outside matters, as it is to be outside for the matters inside. Nevertheless, the murderer is within 100% of possibilities to be deducted. Who was the murderer?