2007 Grand Prix GT

Wife was driving the GT when it suddenly lost power steering and the check charging system light kicks on. Gets it to a parking lot to find that the accessory belt had slipped off and is twisted. I get it home and see oil spray on the passenger side firewall in line with the belt. Also oil residue on one of the pulleys, the tensioner assembly, and the hoses coming from the tensioner assembly. Any idea what this all could be? At first I suspected a pulley, but after seeing the oil, I'm not sure. Read a few threads about how to check the tensioners, they seem to be spinning without any noise. Any questions, let me know.

Thanks,

Camrin