Three civilians and a police officer were killed Wednesday in a "shooting incident" in northern Wisconsin, Everest Metropolitan Police Chief Wally Sparks said.
Police said the shootings occurred at three locations in the Wausau area.
The officer, from the Everest Metropolitan Police Department in Schofield, was killed in the line of duty, Sparks said. The name of the officer was not released.
"This was one suspect, at this point in time. He has been taken into custody," Sparks said at a media briefing where he did not take questions.
Sparks did not provide a possible motive for the shooting, and said the Wisconsin Department of Justice's Division of Criminal Investigations is handling the investigation. Jason Smith of the DCI said the investigation is complex.
It is not clear precisely where the four fatalities occurred.
CNN affiliates WJFW, WAOW and WSAW reported the shootings took place at a bank in Rothschild, a law office in Schofield and an apartment in Weston.