I'm a student of the theory to wait until there is no possible way to miss. Then, and only then, fire one shot into the brain. I'm also a realist, and wonder if I could really hold fire and stand there until he's that close. With a double, I'd certainly save the last one for inside of 5 yards. From the photo, I'd be somewhere red/green, probably closer to green. Missing high does you no good. Missing low might still work. The upper spinal cord and skull base are just as good as a regular brain shot. Head down would be easier.
They can move incredibly fast, and working a bolt under stress can cause certain complications. Right now, I'd probably have a CZ550 .416 Rigby in my hands, loaded with 400gr solids, either Barnes or CEBs.