Maybe it is the way the pictures are taken, but doesn't the barrel wall look thin compared to, lets say, the thickness of the wall at the choke?

The lower rib is bent and there is another tear in the barrel also. That is quite a blow. It has to be an obstruction if it bent the rib.

Your friend must have really been focused on his target to not notice all kinds of stuff coming out of the side of the barrel.

So many guns, so little time!