How would you proceed?

Just a heads up, this is a little gross. I work in a call center as a supervisor, recently a manager came up to me asking me to follow up with a call taking rep who is not on my team. I am supposed to follow up with him to let him know that it has been noticed that he is not "cleaning up after himself" (manager's words) after using the bathroom - meaning he isn't flushing #2s and supposedly leaving "used" toilet paper on the floor. They picked me because I am the only male supervisor and they think it would be better coming from another male. If you must ask how we know it is him, he was noticed by our janitor as the only one leaving the bathroom at around the time of the discoveries (this has happened more than several times). How would you handle this in the most HR friendly way possible?