Police say the man forced the woman into the bushes and sexually assaulted her.
The gunman then fled.
Police recovered a BB gun at the scene.
The attacker is described as a white man in his early to mid 20's, with a pudgy build, standing about 5'10" tall with curly dark blonde hair. A sketch has been released and can be seen above.
Anyone with information that could aid in the investigation should contact police immediately.