It was supposed to be "The West Coast Woodstock," a second utopian music festival that would be the Bay Area's answer to the legendary free concert that had just rocked upstate New York three months earlier. But Altamont instead became synonymous with the death knell of The Sixties, a symbol of the darkness that lay just below the surface of the music-loving, free-loving hippie movement.

Today, December 6, marks the 50th anniversary of The Altamont Free Concert, which was scheduled as an all-day festival on Saturday, December 6, 1969 at the Altamont Speedway just outside Livermore. The Rolling Stones, who did not make it to Woodstock, were the headliners, but the remainder of the lineup included icons of the era the Grateful Dead, Jefferson Airplane, Santana, and Crosby, Stills, Nash & Young. It was supposed to be about peace and harmony, San Francisco-style.

But it was something more akin to the Fyre Festival in the chaotic disaster it became — only at Altamont, four people ended up dead.

"The vibes were bad. Something was very peculiar, not particularly bad, just real peculiar," says Jefferson Airplane lead singer Grace Slick in the biography Grace Slick. "It was that kind of hazy, abrasive and unsure day. I had expected the loving vibes of Woodstock but that wasn't coming at me. This was a whole different thing."

Before the concert had a name or a venue, it was just a last-minute announcement by Mick Jagger on November 26, 1969, the day before Thanksgiving. The Grateful Dead and Jefferson Airplane had been trying to lure the Stones out to San Francisco for a joint concert for a while. As Jefferson Airplane's Spencer Dryden told Slick's biographer, "Next to the Beatles [the Stones] were the biggest rock and roll band in the world, and we wanted them to experience what we were experiencing in San Francisco." The Stones had just played the Bay Area, though — they put on a show at the Oakland Coliseum on November 9, just a few weeks earlier. As the Washington Post explains in a recently published retrospective on Altamont, the free concert would serve as "a swaggering response to cranky San Francisco Chronicle columnist Ralph Gleason, who had accused the Stones of gouging ticket-buyers" at the Oakland show. Gleason was just one of many journalists around the country who had been complaining about the band's high ticket prices on their tour that year, so the idea was to close out the tour with a free concert in the Bay Area.

But in giving the Grateful Dead and the organizational team only ten days to pull the festival together, Jagger inadvertently set the stage for the chaos to come. It was initially planned to be a concert in Golden Gate Park — Kezar Stadium had a conflict with a 49ers game, and an earlier plan to have San Jose State host the concert in their stadium fell through because San Jose city officials were fatigued from a recent three-day festival that had been held there. So Rolling Stones tour manager Sam Cutler, business manager Ron Schneider, and band assistant Georgia “Jo” Bergman flew out to San Francisco and secured the Sears Point Raceway in Sonoma County. Only that would end up falling through on December 4, just two days before the concert date, after the owner demanded $100,000 from the Stones up front — the legendary Maysles brothers were in the midst of shooting a concert documentary about the band, and the raceway owners also wanted a piece of the film distribution rights.

So as fate would have it, Altamont Speedway owner Dick Carter offered up his venue, a race track nestled between hills near where I-580 and I-5 meet. The venue itself created a logistical problem — instead of the rise in the land at Sears Point where a stage would naturally belong, Altamont was was all hills with a flat valley in the center where the hastily constructed stage had to go. It was just four feet off the ground once completed, and photos from the event show people crowded right up to its edges all day — some of the eager concertgoers did the drive out to Livermore the Friday night before and camped out to secure their front-row seats by the stage, because there were no gates, no nothing.

That's where the Hells Angels came in. The music community and the hippies of Haight-Ashbury had come to embrace the motorcycle club after they legendarily "turned on" with everybody else at the Human Be-In in Golden Gate Park in 1967. There was widespread distrust of the police, and so regular cops or the Alameda County Sheriff's Department were not an option for security — eyewitnesses say they never saw but maybe two uniformed officers near the venue, where an estimated 300,000 people showed up that December day.

"[The Angels] were always okay, and when somebody would get on the stage and was not supposed to be there, they’d just go over and tell them not to,” says Slick to the Post. “They didn’t punch them or anything. So, we said, ‘We can get the Hells Angels to be the security [for Altamont]."

The Hells Angels' Bay Area chief at the time, Ralph "Sonny" Barger, told Esquire in a rare 1970 interview about Altamont that mostly they were all there for the free beer they were promised by the Stones, and to get to sit on the edge of the stage and hear the show. "I didn't go there to fight," Barger said. "I went there to have a good time and sit on the stage."

But things turned weird early in the day when a member of the second band to play, Jefferson Airplane, got punched by one of the motorcycle club members. Also, just as the Stones' helicopter landed prior and Mick Jagger stepped off, a concertgoer came up and screamed "I hate you!" and punched him in the head.

"Something wasn’t right,” says Graham Nash, speaking to the Post. “The place was shitty. The way they were treating people like cattle was shitty. God bless the Hells Angels, but to put them in charge of security..."

There were other problems created just by the mass of people who showed up. There were no porta-potties. There was no medical tent. A kid tripping on acid ended up drowning in a drainage ditch. Two more people got killed in hit-and-run accidents.

But after Santana, Jefferson Airplane, the Flying Burrito Brothers, and Crosby, Stills, Nash & Young had played their sets, it was the Stones' turn.

Much of what transpired was caught on film by the Maysles brothers, and their footage, ultimately used for the film Gimme Shelter, would temporarily be confiscated by the Alameda County Sheriff's Department.

First, there were multiple scuffles near the stage that led to Jagger and the band having to stop in the middle of "Sympathy for the Devil" and start the song over again. The Angels were beating people with pool cues. That was three songs into the set.

According to Barger's account, the scuffles began when one of the Angel's motorcycles caught fire near the stage. It's unclear if the fire was intentionally set or not, but as he explained:

"The bike had caught fire. The people were packed right up to the stage. So I told them to back up so we can get this fire out. Nobody'd back up. Some other Angels caught what was happening and came off the stage, and when they did, people started backing up.

"Now I ain't saying anything about no Angel hit anybody. I know some of them hit people. But they moved them people back out of the way of the bike. And we got the fire put out. In the process, you know what, some people got hit. And you know what? Some of them people were like maybe them Friday-nighters that got that front row, I don't know, but they didn't want to give up that spot even to put that fire out. And when they come back fightin', they got thumped."

Four songs later, when the band was doing "Under My Thumb," an 18-year-old African American man from Berkeley named Meredith Hunter attempted to rush the stage with other fans. He was high on methamphetamine, had a gun on him, and several of the Angels spotted it. He ended up stabbed in the neck multiple times, and died. The moment is captured in the Maysles' film, but not entirely clearly.

And the Stones played on. It's a creepy thing to imagine. The Grateful Dead, who were scheduled to play last, never went on. But the Rolling Stones played eight more songs. (See their setlist here.) The band later said they were only aware that another scuffle had a occurred and someone was hurt, but they did not know there had been a stabbing.

But as some witnesses describe it, it felt like they were being held hostage and didn't have a choice but to keep playing.

As Keith Richards tells the Washington Post, "It could have gotten a lot worse, man. That could have been a really big disaster. . .  Who knows what else would have happened?"

The Dead's Mickey Hart tells the paper, from his perspective backstage, "I saw Keith’s eyes. I saw Mick Jagger’s eyes. If they had thought about stopping, you know, there would have been a... knife between Mick’s ribs. Or Keith’s, probably, first.”

"Aquarius Wept," was the title of the Esquire piece that would be published nine months later. "The Rolling Stones Disaster at Altamont: Let It Bleed" was the title of Rolling Stone's coverage just a month later.

The epilogue to the story was that Hell's Angel Alan Passaro was found to be solely responsible for Hunter's death. He was tried for murder in the summer of 1971 but acquitted on the grounds of self-defense.

"Nothing heavy goes down without it being some kind of lesson," said the Dead's Jerry Garcia, in a February 1970 interview.

Hunter's sister, Dixie Ward, says to the Post, "How do I put it? Black people have been in these situations a lot of times. And we don’t expect for people to have helped a black person." She adds, regarding how Hunter's name has become a central piece of the mournful narrative of Altamont and the Sixties in general, "I don’t need Meredith to be remembered by anybody but me and my family. I carry him. And I don’t need a crowd to carry him with me."