Hoover Elite II Model # u4689-910 Impeller...

My buddy broke a window in my car and while he was helping me clean it up with my hoover he sucked up a big piece of glass that broke an impeller blade most of the way off. I removed it but now that it's out of balance it's so violent that it's unusable. I can get a replacement impeller but I can't get the old one off. I managed to twist the impeller so that it now rotates on the shaft but it doesn't seem to be threaded and it's not loosening off anymore. I've tried prying it as well but I'm afraid that I'd need to use enough force to damage the motor shaft or the motor housing assembly. I've looked at schematics and can't find anything that actually retains the impeller on the motor shaft. I've run out of ideas on how to replace the impeller in my vacuum. Please help if you've got any ideas. Thanks.