Update as of 07:13 AM EST
Crashed aircraft.
Not a RTO.
Aircraft ended up in a quarry off the departure end of the runway.
Aeroplane went airborne.
All 7 crew members feared dead.
Coroner en route to site.
Zimbabwe based B747 en route stop in Halifax. Destination Spain (nothing other than that as a destination).
CYHZ closed.
All remaining reports, so far, full of speculation and second guessing as you would expect.