Seems you only know this person from online? My advice: drop him as a friend and don't even bother looking back. Liars can never be trusted, period. He won't stop just because of you, or if you bring it up. He'll most likely cover his tracks and will lie even more, covering up all his previous lies. Why would you want to be friends with someone like this? I have dealt with liars and nothing good can come from it. Move on and find someone far better to associate with.