SPX500 - Teetering on the brink.

I'm only about 60% certain that this is indeed an ending diagonal. But it really seems like it's the only count that fits. The part that is not a normal shape is the wave 4 that preceded it. It's really quite shallow. (I didn't mark in on the chart). But what I can't argue with is the tremendously volatile drop from the top which is very typical of a diagonal completion. With that said, this might also just be the top of wave 3 and an additional wave 4 and 5 are yet to come. But at this point I'm leaning towards this being a long term top. So 4035 is where I think all hell breaks loose and it drops like a rock.