Seven adults and one teenager were taken to the hospital with injuries, Wauwatosa Chief of Police Barry Weber said in a statement. The city's mayor said Saturday that all eight survived and "are believed to be recovering."
The perpetrator is "at large," Wauwatosa Mayor Dennis McBride told ABC News.
The Wauwatosa Police Department said late Friday that the shooter was still at large, but added they did not believe it was a random act and may have started as an altercation based on a preliminary investigation.
"We will continue to work diligently to interview the many witnesses, as well as the victims who were injured, to identify and apprehend the suspect," police said.
The FBI is also assisting in the investigation and interviewing witnesses, McBride said Saturday.
The incident began just before 3 p.m. local time, officials said, when officers were called for an active shooter situation at the mall. Witnesses reported hearing up to a dozen gunshots, officials said. The shooter was no longer at the scene when emergency personnel arrived, Weber said.
About 75 officers descended on the scene in Wauwatosa, about 7 miles northwest of Milwaukee. "Police are actively investigating an incident at Mayfair Mall," Wauwatosa police said in a tweet. "The mall is currently closed."
The FBI's Milwaukee office also said it was responding to assist local law enforcement personnel.
Preliminary statements from witnesses indicate that the shooter is a white male in his 20s or 30s, Weber said.
"Investigators are working on determining the identity of the suspect," the police chief said. "Any information reporting the shooter's identity at this time is false."
"We are disheartened and angered that our guests and tenants were subject to this violent incident today," Brookfield Properties, Mayfair's Mall property management company, said in a statement. "We are thankful for our partners at the Wauwatosa Police Department and we are cooperating with them as their investigation develops."
The Milwaukee County Medical Examiner's Office has not been called to the mall.
ABC News' Josh Margolin contributed to this report.