A strong rejection off of the 0.5 fib is considered to be a dead cat bounce. In this case, the price was not accepted back above and therefor further down side (below 0) is quite possibly on the line.
Check Morpheus, showing us the perfect setup for a short.
A key support / resistance flip level for me would be the 3810 area (give or take a few dollars). Lose that and it's mayhem.