More info and photos.
http://avherald.com/h?article=4cb6a09d&opt=0
The placement of the dents on all the fins reminds me a bit of that. Looks to me like something broke off, got wedged under one of those stabilizers, smacking the hell out of every single fin on the way before it was finally thrown clear.
That said anything-metal falling from the sky is dangerous.
In SF, it’s common for car thieves to break windows using a small chip (size of a pencil eraser) of ceramic from a spark plug. The ceramic is super hard but light weight and can shatter a window easily.[1] being hit by it would barely register.