I don't know if I screwed something up but here's what I did:
Alduin was straight up in the air not moving. I did my Dragonrend shout and he didn't come down.
So, I just shot him with arrows until he died (I saw the health marker deplete all the way. His name was in grey.
The other dragon, Para..., came down and I sliced him up and put Dremora on him. I don't think he even had a red health line on him.
I think I killed him because he stopped moving altogether (even after Dremora was gone).

What's wierd is that Alduin doesn't seem to be moving and doesn't come down even after Para... died.
He doesn't move when I shoot arrows at him but he's still throwning down fireballs.

I know some of the console ppl are saving and reloading...and fixing the bug, but I'm stuck here.

Help.