Any player corpse made by accident or design will have 3 options once they stop moving, Loot, Drag or Swap Clothes.
You do not have to be the murderer, but once anyone has swapped clothes with a corpse this option will disappear.
A little advice. Try not to do this within view of others, looks suspicious and you could be mistaken for a traitor. If you are in communication with the other players you could try explaining beforehand.
There is another achievement for killing a traitor as a survivor, swapping clothes and killing the other traitor. Difficult to do unless you are lucky or crazy enough to attack everyone in sight.
Hope this helps, good luck!