Police detained a suspect in a shooting Thursday at a Fifth Third Bank in Cincinnati's Fountain Square, a police dispatcher said.

Details of the shooting were not immediately available, but the dispatcher said the situation is no longer active, and a suspect is in custody.

"I heard about eight gunshots, and I actually got on my knees. I kind of got down on the ground and then all the cops started coming," witness James Walker told CNN affiliate WLWT. "I'm still shaking."

There were no immediate reports of fatalities. The University of Cincinnati Medical Center has received four patients from the shooting, said University of Cincinnati Health senior director Kelly Martin.

"It started out apparently with an active shooter at the Fifth Third tower, there was an officer intervention and from there now it's just victims and things like that," a police officer told a CNN affiliate.

Eric Kearney, president of the Greater Cincinnati and Northern Kentucky African American Chamber of Commerce, was in a board meeting across the street from the bank. He did not hear the shots, he said, but he saw emergency responders wheeling out victims on stretchers.

The motive for the shooting is unclear. Streets and sidewalks around Fountain Square were closed.

"People in the immediate vicinity should remain on lockdown until further notice," Cincinnati police said in a tweet.

Police earlier characterized the incident as an "active shooter/officer involved shooting incident" in a tweet, but did not elaborate.

The FBI has responded to the scene and is assisting Cincinnati police in their investigation, the bureau said.

Developing story - more to come