The shooting happened after police and firefighters responded to a medical emergency around 5:30 p.m. Wednesday at Valley Transit in downtown Appleton, fire and police officials said. Appleton Officer Meghan Cash said there was no ongoing threat to the community, but she didn't say if anyone was in custody.
Tori Mourning lives across the street from the transit center and heard the gunfire.
"I looked up. I heard a pow and I thought it was the lawnmower firing. I heard it again. I looked up because you could see the bus stop from my bedroom window, looked at the tree. I saw the guy shoot a female and she went down. And another shot was fired and there was another male and he went down and I saw the shooter flee," Mourning told WBAY-TV.
Mourning said she yelled for her children as soon as she realized shots were fired.
"I screamed through my house that those are gunfire and everyone get down," Mourning said, "So I ran, and by the time I got to the top of my house to the bottom my kids all ducked down."
A procession was held overnight in Milwaukee as the firefighter's body was brought to the Milwaukee County Medical Examiner's Office. Firefighters lined the street as emergency vehicles escorted the body. The flag-draped coffin was then brought into the medical examiner's office. The firefighter was a 14-year veteran of the Appleton Fire Department.
Fire officials say funeral arrangements for the firefighter are pending and that the investigation into the incident is ongoing.
Appleton is about 120 miles (193 kilometers) north of Milwaukee.