(CNN) -- A shooting at a St. Louis business Thursday that left four people dead appears to be a murder-suicide, a police official said.
The unidentified owner of A K Home Health Care is believed to be the gunman, police said. The others appeared to be employees.
After a review of evidence, including a surveillance video, officers determined there had been an argument in the office of the business, Capt. Michael Sack told reporters.
"Shortly thereafter, gunshots are shown penetrating a wall inside of the business," police said in a statement.
It was unclear whether the "brief" dispute carried over from another day, Sack said.
The victims were two women and two men, described as being in their early 40s to mid-50s, police said.
A semiautomatic handgun was recovered. No other people were injured, officials said.
The shooting occurred at the Cherokee Place Business Incubator, CNN affiliate KTVI reported.
Police have not been able to find any eyewitnesses to the shooting, according to Sack.
After receiving a call at about 1:30 p.m., police rushed to the building, which houses several businesses.
CNN's Elwyn Lopez contributed to this report.