A frantic Travis Scott fan was filmed trying to raise the alarm as a deadly crush left festivalgoers fighting for their lives.
The woman was shown remonstrating with a cameraman at the Astroworld event in Houston, Texas.
Tragically at least eight people have died and 17 were rushed to hospital, 11 suffering from cardiac arrest.
In the clip, the fan was shown waving her arms around and pointing at the crowd after climbing onto a camera platform.
It was shared on Snapchat onlongside the caption: "Tryna stop the show".
An investigation is underway into the fatal incident, with Scott - who was performing onstage at the time - and organisers said to be co-operating fully with police.
A 10-year-old was among those hurt, officials said.
The tragic scenes unfolded on the opening night of the third Astroworld music festival which was being held at NRG Park in Texas.
Scott stopped his show several times and asked security to help fans, witnesses said.
It is not known whether the cameraman shown in the clip was aware of the unfolding tragedy, or if he was able to relay what was happening to organisers.
Officials said a crowd began to rush towards the stage at about 9.15pm local time and revellers began passing out because they couldn't breathe, KHOU reported.
Within 15 minutes, overwhelmed officials had declared a mass casualty incident because there were so many victims.
Houston Fire Chief Samuel Pena said hundreds of people were treated at the scene for injuries.
"The crowd began to compress toward the front of the stage, and people began to panic," he said.
Mr Pena said there were around 50,000 people in the crowd when it happened.
One devastated festivalgoer posted on Twitter : "I saw people die before me and i heard people crying in disbelief of what they were seeing."
The remainder of the festival has been cancelled.
Dozens of emergency vehicles, including multiple ambulances, were on scene. Police said 367 police officers and 241 security officers were on duty at the festival.
Scott's partner Kylie Jenner shared footage on Instagram during the show showing a paramedic vehicle trying to get through the crowd.
Other distressing clips appear to show people dancing on top of ambulances as paramedics attempt to treat those injured.
Aerial footage captured by ABC 13 showed heavy fire and police activity in the area of the event as it wrapped for the night after 10pm.
"I think it's very important that none of us speculate. Nobody has all the answers tonight," Houston Police Chief Troy Finner said.
"If you don't have facts, if you don't have evidence, I'm not going to speak against that. We have hurting families out here."
