AgtSpooky's Hangout

I think the reason that Dean thought that the rapist's impalement was a sign from God was that the three other people had all been stabbed through the heart. Dean stopped Sam, the rapist's would-be heart stabber, and he himself was in a car chase with the guy. Now you would expect at this point that if the guy died at all, it would be in a car crash, or if Dean HAD to kill him, he'd more likely shoot him. But instead, out of the blue, here comes a truck that just happens to have a load of steel pipes, turns in front of the guy, one pipe breaks loose and stabs him through the heart.

That's what I got from it, anyway.