Got rear ended last night

whats going on every one, both the other driver and I are ok.

I was stopped at a light and a guy driving an audi (prob doing 20-25mph) slammed into the back left side of my MDX.

The bumper and middle piece (diffuser thing) are f'ed, but i'm wondering the construction of the rear bumper underneath.

Anyone have any insight as to what could have bent broken under the bumper cover at 25ish mph?