The shooting occurred in the Cherokee Place Business Incubator, a building in south St. Louis that houses multiple businesses.
"The shooter, another man and two women were killed. The man and women were gunned down before the shooter turned his semi-automatic handgun on himself," Police Capt. Michael Sack said.
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 appeared to work in the same business, but he didn't have other details.
"We don't know if this was a thing that carried over into today or was initiated today," Sack said.
An employee of another business in the building heard gunshots and called police.
The building houses businesses that include an attorney's office, a home health care company and an African bazaar.
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