Throwing bottles at performers is a dubious concert-going tradition. Sure, it can be darkly funny in some cases (Justin Bieber), but it can be downright dangerous in others (Tila Tequila at the 2010 Gathering of the Juggalos). Add to the latter list a 1980 Black Sabbath concert in Milwaukee, where some joker in the crowd tossed a bottle at the stage, struck bassist Geezer Butler in the head, and incited a full-on riot.

The riot in question happened at the Milwaukee Arena on October 9, 1980. The night began without incident: Opener Blue Öyster Cult took the stage around 8:20 p.m., and, by all accounts, delivered a stellar set. And then…a nearly one-hour wait for Sabbath. The Sabbath camp later told the Milwaukee Journal that the long downtime was simply part of the tour—both Black Sabbath and Blue Öyster Cult had complex sets to build and strike. Oh, and the tour was named the “Black and Blue” tour, which ended up being about right.

Finally, following the interminable wait that left the crowd of roughly 9,000 on edge, the Ronnie James Dio-era Sabbath got down to business. (Original singer Ozzy Osbourne had been replaced by Dio the year before.) The band played two songs, “War Pigs” and “Neon Knights,” before the lights were dimmed and Butler was struck with the bottle. But was the “bottling” incident a malicious act, or simply an accident? In a 2007 interview with Maximum Ink, Butler wondered that himself:

“It’s all a big misunderstanding, really, The lights were down, first of all, so unless the fellow was some sort of incredible quarterback, I don’t know how he could have hit me on purpose. But I was knocked out, and the band was busy getting me off the stage and to a hospital. When the lights came back up, there was no band on stage. And of course, the crowd freaked out. Someone should have gone out and explained—the promoter or someone. I mean, the band was worrying about getting me to the hospital, you know? So the crowd freaked out because there was suddenly no band on stage, and things got worse from there.”

Purposeful or not, Butler was right about one thing: things got worse from there. Following admonishments from Dio (“We wanted to give a lot for you, but not our blood. If you don’t want to enjoy it, then tough shit!”) and the British band’s road manager (“1776 was a long while ago!”), the crowd lost its tough shit. Chairs, seat cushions, and railings were torn out and tossed at the stage. Windows and glass doors were smashed. Garbage cans were thrown. Fights broke out. Similar to Altamont 11 years prior, pleas for everyone to “cool out” went unheeded.

And then the Milwaukee police showed up in riot gear. The Arena had been cleared out by the time police arrived at 11:40 p.m., though there was still plenty of trouble on the streets. Three officers were injured in the hour-long melee. More than 160 people were arrested—roughly 80 for riot-related charges, roughly 80 for pre-show drug charges. Butler was taken to Mount Sinai Hospital (now Aurora Sinai Medical Center), treated, and released. Total damages to the Arena were estimated at $40,000.

The next day, Police Chief Harold Breier called for a straight-up ban on hard-rock concerts at the venue. A beer ban was put into place for the Arena’s next big show: Bruce Springsteen And The E Street Band on October 14. But, the Milwaukee Journal Sentinel notes: “Neither ban lasted long. The beer soon returned. Among the bands that played the Arena in 1981 were AC/DC and Van Halen.”

As for Butler, he later put the whole thing in perspective, telling Maximum Ink:

“It was worse back in the ’70s, because no one was going through metal detectors and you didn’t have as much space between the band and the front of the crowd as you do nowadays. People threw a lot of beer cans in the ’70s. Once, in San Francisco, someone threw a huge iron cross on the stage. It bounced up, cut three strings on my bass, and the end of it poked me in the eye. Luckily, I didn’t lose my sight or anything. But that was quite an incident.”

Enjoy audio of the riot below. A special shout-out to the lone fan at the 1:05 mark yelling “‘Paranoid’!”