I had quite a similar case when flying from Bogota to Paris CDG: all at ounce, during 8-10 seconds, my A340 encountered really huge CAT.
I was Captain on this flight and my wife chief purser...
It was a night flight, weather forecast on route OK, but very far from my route, there was a heavy tornado.
I felt weather was too calm, when my chief purser told me that all passengers were eating, and then I switched fasten seat belts on, "just in case".
Then happened this incredible CAT I had never met during my 17000 flight hours.
Happily I had only three injured flight attendants.
If seat belts signs had not been swicthed on, I am quite sure I would have landed at Fort of France or Pointe à Pitre, with dozens of passengers very seriously wounded, or even worse.
Two of my three injured cabin crew lost their medic after that flight.