The suspect allegedly left the scene before law enforcement arrived, Grand Chute Police Public Information Officer Travis Waas said during a news conference Sunday.
According to Waas, various law enforcement agencies responded to calls from shots fired inside one of the main corridors of the shopping center at around 15:30 local time at the shopping center.
The department is not identifying the victim at this time.
Law enforcement agents are completing their secondary search in the mall to locate and guide customers hiding during the incident.
According to Waas, investigating officers identified and questioned several witnesses.
Haas stressed that anyone with information about the shooting or suspect should contact the Grand Chute Police Department.