Lahmers said she ran out of the building and hid behind a auto. She didn't know the extent of the shooting.
Police have not released details on whether there have been any injuries.
Police are on the scene of an active shooting in Middleton, Wisconsin. Police set up a perimeter around the building, Madison.com reported.
Four people were wounded Wednesday morning when a gunman opened fire in a small Wisconsin city, police said.
Police and multiple ambulances have responded.
The Greenway Station shopping center next door to the office building is on lockdown.
Middleton police tweeted out a message that says, "Please lock all doors, stay inside and shelter in place until further notice".
When NBC15 first arrived to the scene there were several employees gathered outside of the WTS Paradigm building located at 1850 Deming Way in Middleton. She provided no additional information.
Andrew King, an employee at an area building, said he saw a man with a handgun going inside another building.
Middleton is about 90 miles (145 kilometers) west of Milwaukee.
Check back for updates on this developing story.