As much as we talk about water pumps around here...
Dude this is a classic case of a water pump failure. When the warning symbol went red you should have stopped the car, turned off the engine, not driven it and inch further, and called a tow truck. Hopefully you have not seriously overheated the engine and damaged the head, head gasket, or even the block. BMW inline six cylinder engines do not like to be overheated.
If you had bothered to read the owners manual it clearly states that whenever a warning symbol goes red, immediately stop and turn off the car and call for assistance.
Go to the maintenance section of the Forum and search on water pump and read up on what you are up against.