wavexrider, I will try to answer that and see if Royg agrees. This is just for my learning purpose.
Look at SPY 5 min chart between 1 & 1:10 there were 2 large red price bars and large red volume bars (on Hillary e-mail news)
RSI dropped to 30
Williams dropped to -80
Chi osc, MACD, Stoch all dropped and pointed down.
There was a re-trace in next 5 min candle 1:10-1:15. I believe he probably bought on that retrace.
Hard part is when to sell as chart was not giving clear indication as far as I can interpret. May be after 2 pm when volume kind of subsided and there was large white price bar after doji and Chi osc, MACD, Stoch were turning up.