Un-freaking-believable...

That's crazy. My bp once drowned a rat and I thought that was odd.

Wow; your boa is smarter than most, I would say! Maybe it mistook the side of the cage for a part of its body?
I had a BP constrict using the last third of its body before (as opposed to the upper body/head/bec area they usually constrict with.) Like the tail was a rat-trap just waiting to be stepped on!