Chicago police say they believe an armed man dressed in black somehow hid and lay in wait inside a popular Wrigleyville tavern before making an attack on the manager.

Officers say the armed robbery occurred early Friday morning, about a half hour after the Cubby Bear had closed for the night.

The manager, described as a man in his 30s, was reportedly hit on the head with a gun after being tied up. He escaped when the gunman left to search the bar's office.

The manager was treated and released at a local hospital.

No one was in custody as of Friday night.