AUSTELL, Ga. -- A $5,000 reward is being offered for information in the case of a teenager who was severely beaten outside an amusement park.

Derrick Boazman, a local radio host and former Atlanta city councilman, joined state Sen. Vincent Fort, community activist Michael Langford and Cobb County Commissioner Annette Kesting in announcing the reward Saturday as Joshua Martin's condition was upgraded from critical to serious at Grady Memorial Hospital.

Martin, 19, suffered head injuries July 3 in what witnesses said was an unprovoked attack by a group of at least 10 males outside Six Flags Over Georgia. Martin, his brother and friend were walking from the amusement park to a nearby bus stop when they were assaulted.

Their attackers escaped on a bus. Cobb County police are investigating but have yet to make an arrest.

Community leaders planned to contact management of Six Flags to set up a meeting to discuss security at the amusement park and the areas around it.

Six Flags officials said last week the attack occurred outside its gates.

Commissioner Kesting said that unless the park increases security, she will ask that its gates be closed.

"I'm looking for Six Flags to be cleaned up," she said.