Did any of the barrels break open?Given the clean, sheer break from the (m)other structure, it suggests that the storage decking in the addition failed. The other giveaway is/are the horizontal lines on the exterior of the (m)other structure, suggesting that when originally built, 2"x 4" lumber was used to "kick-out" the exterior sheathing.
I'd be interested to learn what, if anything, was used to tie the new structure into the original one. Whatever they used was poor/non-existant. The surviving barrels are now thankfull.