Two men were injured: one from a gunshot wound to the arm and another with a shoulder injury not from gunfire, police said.
Neighboring restaurants said they are now taking extra precautions after Sunday's incident.
Aaron Prunty, who works at Mister Taco Bar directly behind Jack's Apple Pub, said he was there the night of the shooting and said Mister Taco Bar has now hired a security bouncer.
"All of a sudden, I saw cops everywhere," said Prunty. "They were running towards here at the bar explaining what had happened, two minutes later they blocked it off like a stand off. I was nervous, I didn't know what was going on."
Prunty said he's seen fights here and there in that area, but nothing like this.
Appleton Police and Jack's Apple Pub made no further comment Monday.