Why is my power window motor running continuously?

I have a problem with the driver side power window on 2003 Element. The window went down but will not return. The odd thing is that the window motor seems to be running regardless of whether the switch is activated. In fact, once I stopped and turned off the engine, and even accessories, the motor continued to make noise so that I had to pull the fuse to get it to stop. What could be the problem with that window motor continuing to whir?