This sounds plausible. From the little I know about carbon fiber, in the event of failure, it's usually the resin shattering. The fibers then just return to their normal state of, basically, fabric.
In this case, the resin failed, the fibers turned back into fabric and the end caps accordioned in. 5 or 6 human bodies got compressed into less than a cubic yard.
Since human bodies are 80%? water, and water under 6000Psi on loses approx 1% in volume, meaning if they started out at 1 sq yard, I would have to agree with you.
