Darius Miller tried to stop a group of men from taking photographs of the mayor's daughters and a third woman. Police said they are trying to trace a group named 01 Entertainment which has surfaced in online discussions of the assault, The Atlanta Journal-Constitution reported.
The group posts pictures and videotape on the Internet, investigators said.
"We're investigating to see if it's a tangible group," said James Polite, a police officer and spokesman for the Atlanta Police Department. "It's a name that has turned up several times."
Miller is a well-known trainer with celebrities among his clients. Franklin, who was skiing in Colorado with a grandson, said she did not know him personally but worried about his condition.