This is what was actually stated:
While holding at flight level 220, the flight crew received a stick shaker activation and detected airframe buffeting.
When did it turn into an encounter with severe turbulence? Lets rewrite Derfred's statement of fact with the real facts and take a different point of view.
1. The stick shaker activated and theaircraft encountered airframe buffeting while in the hold at FL220.
2. A .
3. Autoflight was disconnected.
4. Some passengers were injured.