Is your e-brake stuck? That sounds like it
Basically once the pads are worn down it trips the sensor and throws that light.
Not sure if this helps, but I had the same issue. Turns out the brake pads have a sensor on them that trips that light when the pads wear low (some say when there is ~30% left IIRC). More than likely however, the wire broke causing the light to come on. You can often take the pad wires, pull them off the pad and twist them together.