Authorities identified the alleged shooter, who died of a self-inflicted gunshot wound, as Geddy Kramer.
Police said Kramer opened fire at the facility Tuesday morning in Kennesaw, injuring six people. They said they can't speculate on the shooter's motive.
The contents of the note Kramer allegedly left behind were not released.
Officer Mike Bowman said police also discovered the box for a shotgun Kramer purchased before the shooting.
“We do know the shotgun was owned by the suspect,” Bowman said. “We’re trying to lay the foundation for what happened."