That was his way to break up with you.
He said he loved you -- yet he let you "accidentally" stumble onto this conversation with another woman.
Likely, he sensed you loved him, and he wanted distance, so he confessed falsely love for you, but then made sure you saw that he was either a player or involved with someone else. It is a bad tactic which devils use a lot.
The net effect is you leave him, feeling betrayed (which he probably giggles over), and also remain hot and bothered because you bought into his act.
I just finished watching this movie on Marilyn Monroe. She was this way. A predator. In the movie, this guy who is way out of her league is seduced by her. Everyone warns him, but he does not care and proceeds on. He is not even very good looking. 
It is highlighted in the movie that she is an incredible actress. The director directing her is angry at her for being a bad actress, though the audience is left wondering, "If the director is a better actor then she is, why does he find himself unable to act another way towards her which would elicit better results from her". At the end of the movie, the audience learns that Monroe is playing everyone, while pretending to play no one. And the secret of her great talent is her own incredulity with the world and her own existence. Because she really believes nothing, she is a super actress.
The point is there are people like her out there. A lot of them are guys. You can tell yourself you can survive or escape such predators, or maybe chain them down, but even if you ever chain them down a little? They will just let you to make you feel in control, so they can finally swoop down for the kill.
Clues are very simple as to who they are and their true nature.