I think it's someone who can't lift her easily. Wouldn't be able to get her body into the river without some help - which, I guess, is the tarp in this case. And it's not even a matter of just shoving her body off the bridge and into the river either. They had to find a way to set it so she was properly faced up and holding the sword for whatever reason. Some sick form of respect maybe.

[ who the hell knows ]