Aztek electrical problem

Toward the end of my 55 mile morning commute the battery warning light of my 2001 pontiac aztek came on. A few minutes after that the anti-lock warning light and then the brake light also came on. I couldn't pull over at any time and was nearing my destination (within 5 miles) so I powered on. Next, a "security" message lit, all the dash lights flashed, and then all the gauges and lights died. I pulled in the lot (just barely) and shut it down. Dead. Ten minutes later I had full, but short-term electric power - not quite enough to start it.
are these symptoms of a failing alternator or voltage regulator? At 260,000+ miles, I suppose i'm due to replace either.