I was trading S&P's back in 1987. I remember the crash very clearly. On Friday October 16 I told my clients that the worst was yet to come, but of course I did not anticipate the crash that developed on Monday, October 19.
However my bearish assessment then was based on the simple fact that the market had been going down without any push from negative news. Indeed, after the crash many commentators observed that there was no news that would have justified such a big drop in so short a time.
The situation now is completely different. The market has been going down but it has been pushed by an unrelenting stream of bad news. This is not the stuff of an imminent crash. The news has been baked into prices already. Something much worse than is already known or anticipated would have to happen to drop this market a lot from here.