No one was injured or in custody as darkness fell.
The chief's statement appears to bear out reports from a woman huddling in a home basement near the standoff scene. She told her husband she heard "a ton of gunshots" at mid-afternoon.
"My wife just heard a ton of gunshots," John Shoen, pool manager of the Mary Robin Brigham Aquatic Center in Berwyn, e-mailed a reporter at 3:24 p.m. "She is on Logan Street in the basement of my sister's house with my son. She called me on her cell phone crying."
Shoen said his wife and son were in the basement at 713 Logan, maybe 10 houses from the Logan Court Apartments where the standoff was occurring.
He said he told her to stay there to avoid any stray bullets.
The report of gunfire came after officers deployed a flash-bang device at about 2 p.m. A helicopter was on standby, as the drama unfolded.
The incident began at 7:35 a.m. when police were called to the complex at Logan and Gay Streets to handle a disturbance. While speaking with a resident, "a gunshot was heard from inside of the apartment building," Flanders said.
It wasn't clear who was shooting or where the shot came from, Flanders said. Police cordoned off the area and evacuated anyone who might be in danger.
Flanders said at 11:15 a.m., Pottstown officers and Chester Montgomery Emergency Response Team members began a systematic search of the B building and were able to figure out where the shots had originated.
As they negotiated with the man, the shots rang out at police from inside the man's ground-floor unit in the B building.
The SWAT team, known informally as CMERT, is highly trained to respond to high-risk situations, including those of barricaded individuals.
Complex residents said they believed that the shooter had fired at the door of the maintenance man's quarter's in the B building Monday morning, and that the same gunman had been the focus of a police response two weeks ago, but police would not confirm that scenario.