Electric system

My 2004 Elantra GT has just lost all electic power and stopped running. I seems to have been a somewhat gradual draining: first the sluggish start; then, while idling at a stop, the radio shut off; then the electric windows wouldn't activate; the dash instruments froze; and the engine began to stall. I was able to get the car home (2 miles) and when it was idling in the driveway, it stalled out completely and, of course, would not restart.