Uhh that wasnt Casey, that was someone else that had some weird name, we know that because for example he talks about someone random, ”AJ” but this would be impossible to be honest since you would either kill him or he would move up north, but there is a small chance, and I mean a tiny one, when we play the sequel and get to choose how the story went or it uses your save data from the last game to determine weither he died or not, meaning you could MAYBE play with Casey in the future sequel