My chevrolet pickup just died on me but before it did battery amps drained slowly while driving in town...?

My chevrolet pickup just died on me but before it did battery amps drained slowly while driving in town... It was at night and I could see my headlights dimming and in a matter of an hour I could not see anymore illumination from headlights and my lights inside and even my radio started dieing so i had to cut off my headlights and drive with hazards so I could get lights on my dash to see what speed limit I was driving.. Right before I got home it cut off completely and I coasted in to driveway... Now I am left trying to figure out what went bad on me? Any ideas?