Death came to Altamont before the concert even began.

The “Woodstock of the West” was not ready on Dec. 6, 1969. Just hours before, the massive concert had no home. Golden Gate Park dropped out due to logistical concerns almost immediately. When Sears Point took over, there was an alleged kerfuffle over distribution rights; the Stones were being trailed by documentarians, and the free concert was set to be a highlight of the film. The Stones’ rep said the Sears Point ownership demanded a cut of the distribution rights. The band declined.

On Dec. 5, an offer was made by the owner of Altamont Speedway in Tracy. Within hours, the equipment, stage and crews were rushing from Sears Point to Altamont.

There was a mad dash to get to the patch of dry, brown land. As 300,000 concert-goers rushed the area, a 30-mile traffic jam gridlocked 580 and the surrounding roads into the speedway. Thousands abandoned their cars and started walking.

On the way in, a young man fell in an irrigation ditch. He drowned. His death was the first of four in the coming day.

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Grace Slick had an eerie feeling right away.

"The vibes were bad,” the Jefferson Airplane singer would later say. “Something was very peculiar, not particularly bad, just real peculiar. It was that kind of hazy, abrasive and unsure day.”

Because of the last-minute frenzy, the Altamont Free Concert was hardly in a state to host hundreds of thousands of fans. For a while, a thin rope separated crowds from the stage. But that soon disappeared, and fans kept wandering up to touch, talk to and sometimes assault, performers.

Here, the violence began in earnest. Slick told Rolling Stone in 2014 that hiring the Hells Angels as concert security was partially her idea.

“[Jefferson Airplane co-founder Paul Kantner] and I were talking to [Mick] Jagger about how we’d done a bunch of stuff free in Golden Gate Park and the Hells Angels had been our security,” Slick said. “And they never hurt anybody. And they were good at it because people were afraid of them. So we said, ‘We’ll get the Hells Angels to do security,’ and Jagger didn’t know and said OK. But it turned out to not be right. There was speed and alcohol and those two things are God-awful.”

Alcohol played a key role. In the days after the fiasco, multiple members of the Hells Angels said they were paid by the Stones’ team in beer.

"They said, 'All you gotta do is just keep people off the stage,'” San Francisco Hells Angels chapter member "Flash" Gordon Grow told the Washington Post. "We said, 'Yeah, no problem. We can do that.' They asked us, 'What do you want for that?' We said, 'We're not cops. We're not security guards. Just give us some beer.' They said, 'OK.'"

"That's where it went wrong," singer-songwriter David Crosby, who also performed that day, told the Post. "Hells Angels don't do security. Hells Angels fight. They like to fight. It's part of their M.O. They fight all the time. They're good at it, OK? If you don't want the tiger to eat your lunch guests, don't invite the f—ing tiger to the lunch."

Carlos Santana, then just 22, paused his set during the first song as a fight erupted near the stage. It was a harbinger of things to come.

By the time Jefferson Airplane took the stage, the crowd — and the Angels — were drunker, rowdier.

“I didn’t have my contact lenses on,” Slick said in a Rolling Stone interview. “Or maybe I didn’t have them at the time. I couldn’t see anything. I saw bodies moving vaguely over on my left, which is where [Jefferson Airplane front man Marty Balin] was, and I went back to the drums and said to Spencer [Dryden], ‘What the hell is going on?’ And he said, ‘The Angels are kind of beating up Marty.’”

On the ground in front of the stage, Balin had just been knocked unconscious by a member of the Hells Angels.

Word got to The Grateful Dead, who planned to play their set later in the afternoon. Upon hearing Balin had been assaulted, they decided to leave. On another part of the Altamont field, the Rolling Stones landed in a helicopter. They were immediately surrounded by throngs of fans, one of whom strode up to lead singer Mick Jagger and punched him in the face, a moment caught on camera for the documentary “Gimme Shelter.” Jagger was hustled away by his security detail.

The tension built.

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There was a 75-minute wait before the Rolling Stones went on stage. Over an hour more to drink and stew.

From the moment the band took the stage, it was chaos. “Gimme Shelter” shows the scene: Jagger trying to sing, Hells Angels and fans jawing, an atmosphere about to boil over.

"Listen, man," guitarist Keith Richards can be heard saying. "Either these cats cool it, man, or we don't play."

Jagger stopped several times, begging the crowd to calm down.

“If Jesus had been there, he would have been crucified,” he said to the press the next day.

And then it happened: A man in a bright green suit lifted his arm, .22 Smith & Wesson in hand. It’s not clear if he was aiming it at anyone, but an Angel rushed at him, hunting knife held high.

Jefferson Airplane was leaving Altamont in a helicopter as it happened.

“Geez, it looks like somebody got shoved or stabbed down there,” Kantner remarked.

Meredith Hunter, 18, was dead, stabbed by Alan Passaro.

The Stones didn’t know anyone was dead. They played on, a moment immortalized with great scorn by Don McLean in his classic song “American Pie.”

“And as I watched him on the stage, my hands were clenched in fists of rage,” McLean wrote. “No angel born in heaven could break that Satan’s spell. And as the flames climbed high into the night to light the sacrificial rite, I saw Satan laughing with delight the day the music died.”

The Stones finished their set; Jagger later said they were afraid if they stopped, a full-scale riot might break out.

That night, as the crowd slowly dispersed, two men were killed when a car ran them over as they huddled around their campfire.

The fallout lasted for years. Some was immediate, like the outrage of local ranchers, who suffered tens of thousands of dollars in damage to their fields. Fences had been torn down and grazing fields for cattle were trampled beyond use. Others were longer lasting. The next year, Passaro was tried for Hunter’s murder. Footage from "Gimme Shelter" was shown at the trial. Jurors decided Passaro had acted in self-defense and he was acquitted.

1969 birthed Woodstock and ended with Altamont. As time went on, they felt more and more like bookends on a generation.

“They said Altamont was the end of an era, which more or less is true. It coincided with the way things rise and fall,” Slick said. “Everything does that. Look at the Roman Empire. Sometimes it takes two years, sometimes it takes 500. Everything is born, rises and then dies.”

Katie Dowd is an SFGATE Senior Digital Editor. Contact: katie.dowd@sfgate.com | Twitter: @katiedowd