I killed our Yucca???

I don't know how I managed to do it, but I killed one of the yucca plants we've had for many years. The one stem is doing fine, but the one in the background doesn't have any more leaves on it. I think it must have been over watered, or didn't like being near the window in the cold. I think I will have to do some surgery to remove the dead one and maybe get a replacement.