Bad Battery or Bad Alternator?

Okay. My little 96 Ford Escort has been running fine. However, tonight after work, with the car sitting in the parking lot at my jobsite for 8 hours, the car started up no problem. I drive about 2 miles to a convenience store, go in the store for like 2 minutes, come back out, and try to start the car… It's TOTALLY dead. Radio won't even come on.

So, get it jumped, it starts right up after connecting the jumper cables. Drive 20 miles to my home, no problems, and as soon as I get home. I turn the ignition off… And immediately try to start the engine again. Nope. Dead. Radio won't even come on again!

Just seems weird that this car has went from running and starting perfectly fine to this "totally dead" crap so quickly.

So. What are the odds here? I know I can have the battery and alternator tested. But let's see who is right and wrong. What is MOST LIKELY the problem?

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