A motive for the mass shooting is not yet known.
Federal and local officials responded to calls of an active shooter, with dozens of police vehicles and ambulances rushing to the scene.
"I'm not looking back, I'm running as fast as I can".
Lahmers told the Associated Press she ran out of the building and hid behind a vehicle. She said the shooting was "totally unexpected".
Still, Stubbs says she felt humiliated and degraded.
At least four people were wounded - none fatally - during a shooting at an office building in a suburb of Madison, Wisconsin on Wednesday. "We have a good group". He said he then saw people running "full sprint" away from the building.
According to the Dane County Communications Center, dispatch received multiple reports of an active shooter in the 1800 block of Deming Way.
Middleton is about 90 miles (145 kilometers) west of Milwaukee.
Keely Arthur of CNN affiliate WISC said about 50 police cars and the Federal Bureau of Investigation are at the scene.
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The Greenway Station shopping center next door to the office building is on lockdown.