BIRMINGHAM, Alabama -- A young man is undergoing treatment at UAB Hospital after he was shot at Railroad Park in downtown Birmingham at about 7 tonight, according to police.

Birmingham Police Sgt. Johnny Williams said officers responded to the park for a report of a person shot. "They found a young man suffering from serious injuries," Williams said, adding he did not know the individual's condition.

There was no one in custody as of 9 p.m., Williams said.

"We're not sure what events transpired prior to him being shot. We have investigators looking into that now," he said.

Birmingham police investigate a reported shooting that happened at the downtown Railroad Park on Sunday, March 17, 2013. (Martin J. Reed / mreed@al.com)

Although information about the victim was not immediately available from police, some bystanders among the dozens of people who remained gathered around the park this evening after the shooting said a young boy was shot.

Police officers next to numerous vehicles with flashing blue lights stationed around the park established a perimeter and halted any access into the popular outdoor spot. UAB officers assisted Birmingham police at the scene.

Dale Bryant of Birmingham said he was walking at the park when he heard gunshots at about 7:15 p.m.

"I heard six gunshots. I was up walking on the track and the gunshots were over by the skateboard park," he said.

"Everyone took off running. That's how I knew where it was. Everyone started running," Bryant said.

With the St. Patrick's Day holiday and warm weather today, many people flocked to the park adjacent to Regions Field to hang out.

Starr Alexander and Katrina Belvins, both of Birmingham, were at the park with their children when the gunshots rang out tonight.

"I just heard the shots, I grabbed both kids and ran," Blevins said. "It sounded really close."

Alexander added: "They just kept shooting, like they were determined to shoot someone."

When responding to the incident, officers were radioing each other to keep people on scene.

"Everyone, keep everyone in the park. Don't let anybody leave," one officer said on the radio at about 7:25 p.m. "See if we can isolate some witnesses. We've got no one to talk to right now," another officer later responded.

The story will be updated as more information becomes available.

Editor's note: Updated at 9:15 p.m. to include comments from Birmingham Police Sgt. Johnny Williams. Updated at 9:35 p.m. to include video of tonight's press conference taken by staff writer Kyle Whitmire.