You could go through the interior bedroom wall into the space above the camera location, assuming that it is hollow.
Make a hole down low in the bedroom wall and drill with a masonry bit through the mortar.
You will need to make a small hole that would be covered by the camera and use glow-rods or fish tape to fish the line from the bedroom to the camera.
Then run the wire up the bedroom wall into the attic area then to wherever you need for them to go. You will have made some drywall holes but drywall is really easy to fix.
You could run a rg-59 with 18/2 for the camera.
...or you could also run a single cat5e or cat6 and use a pair of baluns for the BNC and power connections. Like these: http://muxlab.com/product?category=cctv&product=videoease-cctv-power-thru-balun&pid=40