Can someone tell me what happened to this bullet?

[cabelasken]

It struck something solid on entry and spun around and went the rest of the way backwards. I had this happen when I was trying to stop a bull that my friend had wounded 3/4 of a mile from my position. I picked up the wounded bull along with another 6X6 and my only shot was a steep downhill going away shot. My bullet a barnes 168 TTSX glanced off the spine and went diagonally thru the elk backwards and lodged in the far side shoulder. The bull dropped at my shot, but was still alive when we arrived at the scene. my recovered bullet looks a lot like yours...

 

[fta0303]

This came from the offside of my 10 year Olds first buck. It's a 200 gr maker from a 300 blackout @1146 fps.

looks like it started to petal out, then the folded-over petal hit somnething hard, while the bullet had gone a bit off axis. Starting t tumble maybe. Interesting photo.