A Wisconsin State Journal report says a man called 911 Sunday about 1:20 a.m. to say his girlfriend had armed herself with a gun. The man fled the apartment.
Police spokesman Joel DeSpain says officers responded to find the woman armed. He says she "failed to comply with verbal commands."
Two officers opened fire. The woman, whose name hasn't been released, was pronounced dead at the scene.
The officers will be placed on administrative leave, which is standard policy after a police-involved shooting.
The state Department of Criminal Investigation will lead the investigation, as per a new Wisconsin law that prevents law enforcement agencies from leading investigations into their own officer-involved fatal shootings.