Last time it happened, in October 2014, the Fed helped by suggesting won't end (which eventually it did..)
1. The squeeze I mentioned in my Weekly Markets Analysis - Price was squeezed between the 200 line (support and the 2100 with the 50 line (resistance).
2. The breakdown and the close below the 200 line.
3. The 200 line was tested from below and held as resistance for the time
The RESULT - 100 Points decline in $SPX