New serpentine belt smoking and getting chewed up

Just had my serpentine belt replaced in April of this year. I’ve got 128 miles on it since then. I don’t drive the car much, and it’s actually sat for a few weeks since I last started it. But I started it up today…it didn’t want to start at all initially but finally did, and immediately started smoking. Smelled like burning rubber, and sure enough when looking inside, it looks like shredded rubber sitting on the alternator pulley.

So, my question is…what’s going on? 😄 I guess my only option at the moment is to tow it back to the shop that installed the belt and have them check it out. Don’t want to start it again, that’s for sure. I lack the tools (and experience) to replace the belt, but being a new belt, I have to believe there’s a larger issue here.