As rapper Travis Scott took the stage on 5 November at music festival Astroworld in Houston, Texas, concertgoers’ excitement quickly turned to panic after the crowd of 50,000 people started to surge forward—crushing hundreds and killing eight people.

Attendees collapsed, struggled for air, and lifted unconscious people up so the crowd could surf them to safety. Hundreds of people were treated for injuries at the concert venue—NRG Park—or at local hospitals. The youngest known patient was a 10-year-old child. The people who died ranged in age from 14 to 27, The New York Times reported.

Disaster struck during Travis Scott's Astroworld performance as at least eight of the 50,000 attendees died and many more were injured after fans surged toward the stage https://t.co/WJP3WzWALP pic.twitter.com/7awM2zhJQS

— Reuters Showbiz (@ReutersShowbiz) November 8, 2021

The event is one of the deadliest crowd-control disasters in the United States in recent memory, but crowd surges are not infrequent. At an electronic dance music festival in Germany, 18 people were trapped and crushed. In 1979, 11 people died as concertgoers rushed the entrance of a Who show, according to the Times.

In a statement on his official Twitter account, Travis Scott said he was "devastated" by the incident at Astroworld. "Houston PD has my total support as they continue to look into the tragic loss of life," Scott added.

The reasons behind the Astroworld surge remain unclear and subject to investigation, and could ultimately be the result of a myriad of factors.

“Surges occur for a few reasons, often in combination with each other,” says Steven Crimando, principal of Behavioral Science Applications. “In concerts, for example, people want to get closer to the stage or artist and continue to push in. The people towards the rear of the surge feel a little give and try to close the gap by moving forward. They don’t realize the tremendous physical forces they are exerting on the people at the front of the surge, where the amount of force becomes irresistible, and they can’t push back. It can happen in a panic when psychologically people believe there is a limited opportunity for escape, and they aggressively try to push forward to get out of danger. Of course, it can be triggered by rumor, as well as real threats, like someone yelling ‘gun.’”

According to Reuters, fans reported being crushed and trampled during the day before Scott took to the stage, and they were already on edge and throwing water bottles when faced with chokepoints at a COVID-19 testing center and merchandise sales areas. Fights broke out. Hundreds of people required medical care throughout the day. A countdown clock signaled that Scott was about to perform, pulling scores of people to the stage in quick succession.

Although the festival organizer, Live Nation, brought in 528 Houston police and 755 private security personnel to staff the event, the chaos throughout the day overwhelmed the facilities and security staff, eyewitnesses said.

Houston Mayor Sylvester Turner said it is too early to determine if the security operation as adequate, but he did say that “we had more security over there than we had at the World Series games.”

Concert organizers prepared two lengthy emergency plans before the show, with one addressing overall response to emergencies such as extreme weather, an active shooter, or a riot, and the other focusing on medical response, the Times reported.

“Based on the site’s layout and numerous past experiences, the potential for multiple alcohol/drug related incidents, possible evacuation needs, and the ever-present threat of a mass casualty situation are identified as key concerns,” the security plan read.

Concert organizers and Houston officials knew that the crowd at Travis Scott’s Astroworld Festival could be difficult to control. The city’s police chief said he visited the rapper in his trailer before the show to share his concerns. https://t.co/vemvsvuOIb

— The New York Times (@nytimes) November 8, 2021

Houston authorities are also investigating reports that some of the injuries at the concert may stem from drug injections. A security officer reported feeling a prick in his neck before losing consciousness when responding to the crush, and authorities administered opioid overdose-reversing drug Narcan (also known as naloxone) to revive him, Deadline reported. By the end of the incident, EMTs on site had run out of naloxone, according to the Times.

“Drugs and alcohol are rocket fuel for crowd risks, and depending on the event, may play a large role,” Crimando says. “They are a contributing factor, but not always causal in crowd tragedies. Planners can’t much control what people ingest before they arrive, but they can be mindful of who they serve if alcohol is sold on site. Planners have to assume there will be significant numbers of overdoses, and high levels of intoxication. This can be magnified by heat—both the weather and body heat—in crowds and made worse. Today, you need a lot of EMS personnel and Narcan on hand at any major concert.”

Specific to crowd surges, security personnel can help limit risk by using different types of barriers to segment a crowd so that it cannot transform into a 50,000-person mosh pit, Crimando says. “Psychologically, when people realize the limits the barriers create, the impulse to push forward is reduced, and if there is a surge, it is contained.”

Event organizers had planned to deploy security personnel along nearby roads, gates, fence lines, and VIP areas, and they set up perimeter barricades such as bike racks and concrete bollards, the security report said. Security personnel were given a list of visible signs that attendees needed medical care—including signs of overdose.

While thoughtful ingress and egress designs and strict perimeter controls are useful for influencing behavior, it is impossible to anticipate all possibilities. “Individuals in the crowd, the artist and the emergency management all have to have clear rules and be in real time communication with each other,” Crimando says. “The artist can easily misinterpret behavior they see from the stage, the emergency teams have limited visibility into defense crowds, and event goers have no guidance on what to do if something goes wrong.”

In Houston, Travis Scott saw the first ambulance arrive from his position on the stage and paused his performance for a few moments before resuming, urging the crowd to make the “ground shake,” the Times reported. The concert continued for another 30 minutes while the surge continued to crush attendees and first responders struggled to access people in need.

“Whenever I teach crowd safety to first responders, it is usually the first time they are getting any education on the topic,” Crimando says. “The artists need to understand their responsibility, as well, and have instruction on how to reduce crowd crush scenarios, and concertgoers should have clear instructions before a crush on how to safely escape. Just like there are signs along the beach on how to escape a riptide, posters around the venue on how to escape a surge or crush would be really helpful.”

Astroworld victims sue Travis Scott, concert organizers after crowd surge deaths https://t.co/NukUe7mnbe

— USA TODAY (@USATODAY) November 8, 2021

The first three lawsuits have been filed in the aftermath of the incident, with lawyers calling the festival a “predictable and preventable tragedy” and accusing the defendants of negligence and gross negligence, claiming the crowd surge and resulting injuries and deaths were the result of “a motivation for profit at the expense of concertgoers’ health and safety,” USA Today reported.

The second day of the Astroworld Festival was canceled.