It all depends on the available light. That said, I would guess that:
- Aperture - for the lens mounted, wide open. I doubt that you would have a choice here, stopping down would only artificially increase the ISO, and / or slow down the shutter speed
- ISO - gee, start at 800, if not 1600 or so - perhaps even higher. It just depends on the light. This is going to be a balancing act with shutter speed. You are going to want to minimize the sensor noise to the extent possible.
- Shutter Speed - This is again hard to say, other than as fast as possible. Just keep walking the ISO up until you get a shutter speed sufficiently fast. Probably on the order of 1/100 sec to freeze the subject. You are going to have two things working against you here, 1) being movement of the object in the image; and 2) camera movement - especially if hand held. It would probably be better with some mechanical support - a tripod or better yet a monopod. This would minimize the potential for camera movement, so you could focus on getting something fast enough to freeze the movement of the subject(s) in the image, while keeping the ISO sufficiently down to minimize noise and increase image quality.
- Auto Focus - With the K5II - this should be the only thing in your favor. Rumor has it, that it will focus in complete darkness.
That is all, that comes to mind. You just have the 3 parameters to balance. Good luck, and post some images along with how things turned out - what you had to do, in order to adjust to the light that was available.
Some additional thoughts - it might be interesting to have some movement in the folks in the image. Motion in hand movements, rifles spinning, etc. Its really the call of you the photographer. Its assessing the environment and the situation along with your location, and trying to make the best of it. Also, taking some creative license in making the best of an imperfect situation. When given lemons - make lemonade.
One other thought comes to mind - normally I would think that one of the averaging modes for the light meter would be best, in order to get a good uniform set of light across the frame. That said, you might also consider spot mode and see how this would work out. This way you would emphasis the light from the spot that you are focusing on and meter for that, letting the rest of the frame just be as it is. Just a thought.