The male shooter is among the four dead, police say. Officers recovered a semiautomatic handgun from the crime scene.
St. Louis Police Capt. Michael Sack said the dead were in their early 40s to mid-50s.
“We don’t know if this is a prior thing that carried over,” Sack said.
Michael Graff, who has a law office in the same building, said the health care business was owned and staffed by Somalian immigrants. He said he had heard heated arguing there on past occasions. Graff was not in the building Thursday when the shooting occurred.
Sack said the shooter appeared to be an employee or owner of the health care business, and that the victims were employees. No one else was injured.