I say, also, with 99% certainty it's the alternator. If it dies while you are driving, it's the alternator. If it doesn't start, it's the battery...generalizing in your case of course. The battery starts the car, once it's started the alternator takes over. If your alternator can't handle it, then it falls onto your battery, so you can run it for a little bit on a full battery, but not for long.

Same thing happened to my brother's civic. How did we get it home? I followed him with my CRX and when his car died, we swapped batteries to get him all the way home. Funny now, but not at that time.

You might have to change the battery too, since you just drove it until the car died, it drained the battery to nothing.