It was one of those "Let's make it look there's going to be a sequel, even though there isn't going to be one" endings.
It took me so long to get the reference. "Cain and Abel". XD
It's a show that rips so much from the Bible and I didn't catch that easily.
I laughed at how much this coped Trigun as well but I remember noticing that earlier, CK.
Do the manga and novels follow the same plot?