Woke up this morning and rear brake lights are on. They won't shut off?

I've had this happen a couple times on my 2001 Hyundai Santa Fe. The (momentary contact) switch that the shaft of your brake pedal is probably loose. When it's loose, it allows the brake lights to be on, even if the ignition is off and you're not in the car. That will quickly wear down your battery if not fixed immediately. With a light and a small crescent wrench at hand, you'll need to contort yourself into a position where you are lying on your back looking up at the shaft of the brake pedal. You will see the switch that contacts it. You simply need to position the switch in or out until it is engaged (pushed in) enough by the spring-loaded brake pedal shaft to turn off the brake lights, and then securely tighten the nut that holds the switch in that position. Once tight, check to make sure your brake llights are off. If not, try this procedure again, moving the switch so it sits closer to the brake pedal shaft in it's resting position. The correct position will turn off the brake lights when the pedal is not being pushed down.