October 2, 2017 11:13 PM EDT

When a gunman opened fire at a country music concert in Las Vegas, killing at least 50 and injuring more than 200 more, concert-goers ran for safety. Backstage, the scene was equally chaotic, PEOPLE has learned.

Dan Bilzerian, the social media celebrity known as the “King of Instagram”, was on stage and enjoying his night when the massacre started. “I used to play baseball with Jake Owen when I was a kid,” he tells PEOPLE. “We were on the stage when the gunfire started.”

Bilzerian says it took them about 15 seconds for everyone to figure out what was happening. “It sounded like firecrackers,” he says, “which is what it sounds like when supersonic bullets are flying over your head.”

As people backstage realized that the concert was under attack, everyone scattered. “I was pretty calm, all things considered,” Bilzerian says, “but I definitely ran to safety.”

The carnage was everywhere. Bilzerian says that he saw a female victim lying on the ground. “She was dead,” he says. “She had been shot in the head, and her brain was showing.”

Bilzerian got in his van and took a terrified, injured woman to the hospital. “I don’t know the extent of her injuries,” he says. “She could barely talk.”

When he was safe, Bilzerian made the decision to return to the scene with his own gun to try to save others — but returned to find that law enforcement had everything under control.

“It was a pretty strong wake up call,” he says. “This stuff can happen without warning anywhere. It’s not smart to get caught without a gun.”

Bilzerian says that he would make the decision to return to the scene all over again. “I don’t think it was heroic at all,” he says. “I just wanted to do the right thing.”

How to Help and Learn About Loved Ones

Friends and family are asked to report missing people believed to be connected to the shooting using the hotline 1-800-536-9488.

Anyone with photo or video evidence of the shooting is asked to call 1-800-CALL-FBI.

The city of Las Vegas has established a Family Reunification Center to help connect relatives with the more than 500 people who were injured.

In addition, city officials urged those locally who wish to donate blood to visit one of two donation centers operated by United Blood Services, either at 6930 W. Charleston in Las Vegas or at 601 Whitney Ranch Drive in Henderson, Nevada.

A victims’ fund has been started on GoFundMe by Steve Sisolak the Clark County, Nevada, commission chair. Other groups providing relief include the local chapter of the American Red Cross and the National Compassion Fund.

This story originally appeared on People.com.

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