If it was Jay, what if he was going to meet Ben at the time, and had no idea Lucy would be getting off there - Ben gets spooked by it and attacks her and kills her quite by accident, similar to Heather. That would fit the tragic and sad part

Well, Ben is supposed to return soon. I think it would be a bit of a lazy way to go, I think it would be a bad move to reveal it was a character who wasn't even on screen during her death. It would be lazy as they could make up any reason to kill her in a way. There would be know point for anyone to be acting shifty or be having arguments with her or hating her.

Yeah, I agree, although that seems to have passed a lot of people by stating that it must have been Nick