'I saw a dude walking with a gun inside the building, ' King said.
The woman was seeing being held up as she was taken from Esker Software in Middleton, Wisc., Wednesday morning.
Wisconsin police are asking everyone near the scene of an reported active shooting to hunker down until further notice. Police have set up a perimeter around the building.
The shopping center next to the building, Greenway Station, was locked down at the direction of police, according to the center's general manager Corey Kautzky.
A large number of emergency services, including a SWAT team and multiple ambulances, responded to the shooting.
A bird's-eye view of North Carolina under water
A state of emergency was declared in Tioga County due to flash flooding, according to the Ithaca Journal on September 18. The death toll from Florence, which came ashore in North Carolina on Friday, rose to 31 on Monday.
Dane County Sheriff's Office spokeswoman Elise Schaffer confirmed there was an "active shooter situation" and said her office is assisting Middleton police. "Avoid the area north of West Campus into Middleton". Authorities told NBC 15 that the scene has not been cleared and it is still active.
The call of shots fired inside the building at 1850 Deming Way first came in around 10:30am local time.
NBC 15 spoke to employees who work at a building next door who said they saw employees running from the neighboring building.
WMTV in Madison has a crew on the way and will provide updates when more information is received.