Normally the altitude selector is set for 1000 ft scale over FL100 so once you turn and pull it it'll initiate a descent. The aircraft will go into Open Descent mode which basically means it'll keep a fixed IAS/Mach and descend with engines in idle.
The procedure calls for increasing speed and thus creating a high rate of descent and also using spd brakes if needed and if possible.
If they for some reason selected FL90 or similar and then became incapacitated they would have descended with a fairly fixed ROD to that level and afterwards the aircraft would have leveled off keeping the same speed...