Photograph by Brad Barket/Getty

The reviews of last weekend’s Summer Jam 2015 gushed over Kendrick Lamar’s “lightning-quick flow.” Social media lit up with people tweeting and Instagramming Nicki Minaj’s surprise appearance alongside Meek Mill. But, for many, memories of the night will be punctuated by the high-pitched wail of military-grade sound cannons and the burn of mace. After what was described to me as a “brawl” broke out at one of the gates of MetLife Stadium, in East Rutherford, New Jersey, the gates were shut and the police deployed military hardware to disperse concertgoers.

The concert, which has been held annually since 1994 by the New York radio station Hot 97, is a showcase for some of the biggest acts around. Lamar had top billing, but rumors had been flying about which special guests would show up. Would Minaj make an appearance? 50 Cent? Hours before the concert, people began posting pictures to social media of what they were wearing, and tweeting about how excited they were.

I arrived at MetLife Stadium with a group of friends shortly after seven. The concert had already started. There were three or four hundred people outside the gate, and the doors were blocked. Most were calm and relaxed, even though they were frustrated to hear the crowd roar inside when Trey Songz was announced. We were told by event staff to wait, that there had been a small fight, and that we would all be allowed in once the offending parties had been dealt with. We would be late, but we wouldn’t miss Lamar’s set.

At that point, most people decamped to the parking lot, taking selfies, clustering around cars playing low beats, and enjoying a beautiful June evening. Venders sold nutcrackers, a drink made from hard alcohol and Kool-Aid, and the air grew fragrant with marijuana smoke. Every so often, people would run up to the gate to ask when we would be let in. Soon, we were told: fifteen minutes, forty-five minutes, half an hour—our tickets were still good. My group of friends walked up to police officers standing by the gate, who asked why people like us would want to go to an event for black people. We were all white.

It’s hard to tell exactly when the atmosphere turned. Maybe it was when a woman—presumably one of the event organizers—came out from behind the gates and shouted at us to go home. She wouldn’t confirm that tickets would be refunded. Maybe it was when police arrived in riot gear. Who threw the first punch, or bottle, is unclear. The situation quickly escalated. The police hid behind the gates and began ordering people to disperse. Our chances of seeing Lamar were looking slimmer by the moment. A crowd gathered, and people started swearing at the police. Every so often, a group of officers would run out in a phalanx and grab someone who had been talking back to them. Video footage shows police grabbing a man simply for swearing at officers.

It was at this point that I noticed two squat black police trucks gliding through the crowd around the gates. The trucks are called BEARs, and are thickly armor-plated. The company that sells them, Lenco, advertises them as ideal for tactical and special-weapons teams. The officers inside the vehicles started to test sound blasters called LRADs on the crowd. These sonic weapons were developed in response to the U.S.S. Cole attack, in 2000, and have been used to stop Somali pirates boarding ships off East Africa. An ominous message—“This is a test of the Long-Range Acoustic Device LRAD”—was followed by an ever louder count to ten. The would-be concertgoers started throwing bottles at the police.

A small group of us walked up to the gates to ask the police what was going on. I held up my I.D. and identified myself as a journalist. The officers in front of me raised cans of mace in reply. They wouldn’t mace people for asking questions, would they? After all, they were standing behind gates that were ten feet in height, sporting helmets and plastic shields.

I heard a shout and a click, took a gulp of air, and closed my eyes. Then my face and hair and sweater were wet. My lungs and body started to burn. I held my breath and started running. People around me were screaming. I opened my eyes and was hit by a cloud of tear gas. I heaved shallow, gristly coughs as I ran clumsily forward, fumbling in a mist of hot, red pain. Everywhere burned. And then my ears exploded. The LRAD had been deployed.

Presumably there’s a reason that the police decided that mace and tear gas weren’t enough. At the scene, I tried to ask a Sergeant Wolf (he wouldn’t give me his first name) why the LRADs were necessary; he referred me to the New Jersey State Police public-affairs office. When I later called, I was referred to the department’s Facebook page. At the bottom of a six-paragraph statement reporting that sixty-one people were arrested and ten officers injured, I saw a quotation from Colonel Rick Fuentes, the superintendent of the New Jersey State Police. The release quoted him as saying, “A small group of highly disruptive people ruined this concert for many others. They created a danger to ticket-holders, stadium employees, and troopers on the scene. Our troopers took the appropriate steps to restore order to what was a brief and volatile situation.”

Christian Layne, a twenty-four-year-old who had come from upstate New York to see the show, had a different version. He said that he had saved up while working a supermarket job to buy a two-hundred-and-fifty-dollar ticket, and, when he got to the gate, he couldn’t get in. “I was strafed with tear gas and mace,” he told me. “They treated everybody unfair. They just did that because they were scared there were so many black people around. They were scared of the crowd.” (Hot 97 has said that ticket holders will get a refund.)

Back in New York the next day, still addled, I called Kamau Rashid, a sociologist whose work focusses on race. During our interview, he recalled his student days at the University of Illinois at Urbana-Champaign, and the discrepancy between on-campus events for black students, who were forced to wait in line to go through metal detectors, and fraternity events off-campus, where he saw white students setting things on fire and jumping out of windows. Rashid described what we have seen over and over again in recent months: historically, blacks in the U.S. were seen as objects of “coercive control.” After slavery ended, coercion became coupled with policies of containment and segregation. He said that, for police at traditionally black events like hip-hop concerts, “there’s a perception coming in that they’re not just dealing with revelers; they’re dealing with objects that, absent a measure of coercive control, would become violent.” He said that this mirrors the anxieties that inform policing strategies in traditionally black areas. “There’s a sense that African-American culture is there to be enjoyed, but African-American bodies are there to be contained.”

From news reports, it looks like people who attended Summer Jam enjoyed another year of hip-hop history being made. But the police reaction and the ensuing violence pose serious questions that are hard to answer. Why did the police escalate events? Why did officers deploy advanced hardware against a mostly peaceful gathering? A different kind of history was being written, once again.