I have shot a number of deer with a .22 using subsonic hollow points, the largest being a red/wapiti cross that went 115kg on the hook. That was shot (2x) in the neck, but I had pass through several times with fallow deer shot through the ribs. There isn't much in there to stop a bullet, and if you can see where they run then I expect that it would work ok on deer as large as a caribou. I know that it is not ideal, but I know it works.
On the other hand, what was the point of telling the story in the first place?