Hopefully I'm carrying a fast aiming firearm like a 30-30. I'd shoot at the top of the shoulder or the neck, wherever my sights would fall first. Then I would put another cartridge in the chamber as fast as I could and get ready to follow up. A scoped rifle would be a nightmare at this time. A scope full of brown hair is a bad thing. I'd rather have my 44 mag supper Blackhawk in my hands than a scoped rifle in this scenario.
With a bow, I'd draw and wait until his back end started rising when he started getting up. Then I'd let one go through the lungs. It's ten yards and he won't be jumping the string cause his front end will already be down. That is if he doesn't take off before I get the sights on him. A traditional bow would have the advantage here.
Funny thing is I walked up on a big mature buck during muzzleload season that was bedded down in the edge of a cedar thicket. I crawled on my hands and knees, moved from cover to cover with the wind gusts and could only get to about 50 yards. At one time my feet was past the point of tingly and were full fledged asleep from the akward position of my stalk. I waited as long as I could and never got a perfect shot at him. With little time left to hunt I made the decision to shoot thru what I thought was a clear lane. I missed and still do not know if it was human error or if my sabot caught some brush. I was pretty bummed but did see the buck again not more than a hundred yards from the spot he was bedded down the next day. There is always next year!!