Whilst I wouldn't disagree with booking some profits soon, I don't think we are quite at shorting levels yet. The prior S&P high was 1398, that is quite likely to get challenged, and potentially see a false breakout (assuming it doesn't just blow through the level). I think that would be a better place to short. In addition, with vol coming off and the VIX in the low 20s, I'd much rather buy puts than go outright short. You are very vulnerable to getting squeezed if the S&P spikes to say 1410-20 before falling back.
I think we nevertheless should congratulate the OP for seeing a downmove a good 25 minutes after it started happening.
It must require hundreds, if not <b>thousands</b>, of hours of screen time to obtain that kind of skill. I'm envious.