Tail coming off on rotation?
I'm not an accident investigator nor I care to be one, but it sounds like this A/C was forced off the groung at a speed close to vmu and way below v1. The 747 is capable of lifting of at speeds substantially lower than v1. Based on the stage lenght of the planned flight, I'd say they were fairly close to a balanced field condition (assuming full thrust and full runway lenght). If an un-intentional intersection take-off was attempted, I suspect that they simply saw the red lights approaching and attempted to force the A/C aloft. It appears from eye-witness accounts, that the tail hit an embankment at the departure end of runway, before ripping off. The 74 is a well built bird, but considering its mass, I'm not surpriced that the tail failled as it impacted the embankment...Just my 2 cents...