Atlanta police are investigating a shooting at a back-to-school event Saturday that left a man injured.

The incident happened around 8 p.m. at Coan Park in southeast Atlanta.

Many families told Channel 2's Michael Seiden that they're thankful to be alive after bullets started flying in the park.

Crime scene investigators worked late into the night Saturday trying to piece evidence together.

"Someone fired a weapon that struck an individual in the ankle and that person is stable and being cared for at a local hospital," Maj. Darin Schierbaum with the Atlanta Police Department said. "We do have an individual detained that may be the shooter, and he's being detained for questioning."

Police said the gunman and his 23-year-old victim were leaving the park after attending the Zone 6 Day, which was billed as a community event for families living in East Atlanta and attended by hip-hop superstar 21 Savage.

But as word spread, the crowd quickly grew

“This event was permitted for a couple hundred and it greatly exceeded that," Schierbaum said.

Thousands heard the gunshots.

“We didn’t even make it to the park. It was like a wave. Everybody was just running. You run and then I run. I didn’t even know where we would run,” one woman told Seiden, asking not to be identified.

Many jumped into their vehicles, creating a traffic nightmare.

“We had a number of police resources that were in the area already and started mitigating traffic in park and on foot and in vehicles,” Schierbaum said.

The motive remains unknown, but investigators believe the shooter knew his victim.

Channel 2's Lauren Pozen learned that Santonio Foster has been charged with possession of a firearm by a convicted felon in the shooting.

Seiden said investigators focused attention on a black Ford Mustang Saturday night. Detectives believe the shooter jumped inside the vehicle after he fired shots into the crowd.

Police said several other people received minor injuries while running away from the park.