Following Woodstock in the summer of 1969, another huge concert was held in northern California in December of that year at the Altamont Speedway. Around 300,000 are alleged to have attended. I am always skeptical of announced crowd figures but there was unarguably a huge number of people there.
Believe it or not the Hell's Angels provided security for the event and an Angel stabbed a black man to death near the stage as the Rolling Stones were performing. However the black guy had a gun and was waving it in a threatening way and the Angels did the right thing in taking him down.
Altamont came be known as the anti-Woodstock concert because of its bad vibes, while others proclaimed it the "end of the '60s" in the simplistic way decades and eras are defined. The first video shows the death of the black man while the second one shows some of the mayhem as the Stones, fittingly, were trying to sing Sympathy for the Devil.