Evidently the shaft breaks off from the impeller. If you can pull the pulley out, think that's proof that the pump is done.
Only other really low odds chance is that someone had the belts off recently and put them on the wrong way...like I said...low odds, but it's happened before.
I'm so depressed. No one wants to come see me in NYC: Sat, Oct. 8, 6 p.m. at Greenwich Village Comedy Club.
Mangofy your E46!