It was a historic day on Wall Street. The Dow plunged 10% for its worst day since Black Monday in 1987. The 30-stock index fell 2,352 points —  its largest point drop on record. Meanwhile the S&P 500 plunged 9% to close in bear market territory, thus officially ending the bull market that began in 2009 during the throes of the financial crisis.

Here's what happened: