1x03 The Possibilities

The Preacher confides on the vampire Cassidy about his powers. The two strangers stalking the Preacher are revealed to come from Heaven in search of the "very dangerous" thing called "Genesis" that has taken residence in the Preacher. Cassidy (comically) offers himself as the intermediary between these envoys from Heaven and the Preacher --- for a price: money, drugs, blackies, etc. The Preacher's girlfriend convinces him to search out and kill Carlos, who apparently destroyed their past. On the way, the Preacher runs into a member of his flock --- of whom he had broken an arm trying to protect the man's wife from the man's frequent beatings in the first episode. The man intends to kill the Preacher with a gun; but the Preacher orders him to turn the gun on himself, and almost orders him to pull the trigger, but changes his mind at the last minute, in a show of pity. (The look of terror in the man's face is truly beyond words, as he realizes that he cannot do anything against the Preacher's orders, and expecting to die right then and there). After this, the Preacher gives up on tracking down Carlos.

Who is this Carlos, and what did he do to the Preacher and his girlfriend in their previous lives of crime? All we know so far is a scene where the Preacher is shown with a gun, a woman police officer shot in the head, an a car speeding away from the Preacher and his girlfriend while the girlfriend shouts "Carlos" at the top of his voice.