The shooting happened at about 1:40 p.m. inside the Cherokee Place Business Incubator, the St. Louis Post-Dispatch reported.
The building has been evacuated and police said they were questioning at least three people. At least one man and two women were taken into custody, police said.
KTVI, St. Louis, reported police have recovered a gun and said that there is no active search for the shooter.
Duggar sisters unveil Christian dating rules in new book
LGBT community has 'bullied the American people': Bachmann