i agree with mike, that it is easiest to animate in normal speed. but for the render if you stretch it in post, then quality will go down. you can render the animation out slower with the by frame option. so if you want to render frames 40 to 45 stretched to one second you would render like this:
render -s 40 -e 45 -b 0.25 bullet.mb
and it will render instead of 6 frames 24 frames (for 24 fps, one second, 4 times slower). and then you have to render each snippet seperate - before bullet time, bullet time, after bullet time. and then composite them together with 24 fps.
and for completely freezing the scene, just dont animate anything and only move the cam (but could be problematic if you have time dependant materials).
p.s.: the frame rates are from movies, you might want to adjust it to 25 or 30 frames