A little while ago, I managed to obtain a 104% kill participation while playing a Quick Play game on Lijiang Tower. (It was on July 25, 2016, in the event that was a bug patched afterwards).
How could I attain such a score? If it was accuracy, I could understand that I could hit more than one target per shot, but as far as kill participation goes, I'm not really sure how it was possible.
Screenshot below (from shadowplay video)
I can upload the video for the whole game if needed. It wasn't brilliant but maybe it could help explain how this came to be
Link to the video of the complete game