According to investigators, between 15,000 and 20,000 from the Houston and Galveston areas attended the Texas Beach Party at Surfside Beach.
An online invitation circulated via social media said the party lasted from noon to 7pm Saturday and would have free food and drinks, games and live entertainment. Authorities said they did not have a permit for the party.
Officials believe the shooting is connected to the event. Authorities said the atmosphere there turned violent.
"We let them party as much as they wanted and it got out of hand," Surfside Beach Police Chief Gary Phillips said.
Eyewitnesses told us there were several fights, lots of yelling and people jumping before the gunshots were fired around 9pm.
According to officials, multiple agencies were called to assist, including Freeport police, Surfside Beach police, the Brazoria County Sheriff's Office and DPS.
Traffic going onto and off of the island was blocked, making it difficult for responders to make it to the scene.
Authorities said they initially heard five people were shot, but they only found three shooting victims.
Two of the victims were airlifted to Brazosport Regional Hospital, police said. One male teen from Houston was shot in the buttocks and another man was shot in the leg.
They said the third victim was shot in the throat on the beach. He hasn't been identified, but we're told he was with his family on the beach when he died.
No arrests have been confirmed. Police told us they are still trying to gather information on the suspects.
Phillips said they know people have been publishing photos of the deceased victim on social media, and they will be checking into that as part of this investigation.
Please stay with Eyewitness News and abc13.com for updates on this developing story as they become available.