Police Capt. Michael Sack said the shooting happened Thursday afternoon in a building that houses multiple businesses. The victims' names have not been released. Sack said they appeared to be in their early-40s to mid-50s in age.
Sack said the three victims worked in the building. He did not have any other details about them. An employee of another business heard gunshots and called police.
The street about five minutes south of St. Louis is lined with antique shops, kitsch stores and other shops. Police cordoned off the area around the business.