Re: Motoring along...
"So probably something like tank burst causing debris which took out the first stage."
Another possibility is that rockets tend to depend on pressurization for some of their structural strength, if not all to the degree of the Atlas series of rockets. Poke a big hole in one of the pressurized tanks and the stack will buckle. My money is max Q rattled something loose, the tank burst, and the upper stage collapsed when the tank depressurized. There was a lot of liquid oxygen spilling around the rocket in the last seconds.
Anyway, first person experience with the launch:
I was visiting relatives and got to see the launch with mark one eyeballs. A lot of folks turned out to watch it, but headed in when it got faint - the conditions weren't great for a continuous contrail so it got hard to see near the failure. They didn't find out until half an hour or so later when news started circulating.
I stuck it out (partly because a tree had hidden the first part of the launch and I wanted to see more) and got to see the *poof* at the end, which didn't look like normal staging. I was checking to see what happened on the webcast when the original launch noise reached the house, which was an odd bit of sonic time warp: I was hearing the initial launch noise of a ship that had already blown up.