Local reporters witnessed police hauling boxes of evidence from the gunman's residence.
Police made no mention of any search for a possible second attacker, but warned that the area would remain on lockdown as the scene was investigating.
The chaos unfolded alongside Fountain Square, the heavily trafficked park at the city's center.
Cotter said Newcomer had worked for Gilbane, which has headquarters in Rhode Island and has two offices in OH, for four years, overseeing trade workers.
"This is a horrific incident", Isaac said.
"This is an American problem, that we as Americans must solve by putting ideology last and human life first", said Cincinnati Mayor John Cranley.
The man, who declined to give his name, at first thought it was a joke, but then saw the gunman firing into the bank. He said one investigator warned it could have been "a bloodbath beyond imagination".More news: Pakistan bans first-class air travel by PM, president, govt officials
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The deceased victims were Luis Felipe Calderon, 48; Pruthvi Raj Kandepi, 25; and Richard Newcomer, 64, according to the Hamilton County Coroner's office. Police also hope to get clues to the gunman's movements from surveillance video from the building and outside near the square.
"The shots got closer and closer and closer and closer and that's all you can think about is, I'm next, I'm next, I'm next", Janetta Cook who works at a bakery shop near the lobby told CNN affiliate WCPO.
"These are things we see happening across the country, and we all have to be vigilant and prepared to deal with these situations", Isaac said.
Police say multiple people have been transported to an area hospital but there is no word on their conditions. "After that, I started running", Richardson told the paper.
Ebony Ginyard, who works at a Dunkin' Donuts in Fountain Square, said she and other workers and customers dropped to the floor when the shooting erupted, according to Reuters. (Albert Cesare/The Cincinnati Enquirer via AP) A woman is comforted by authorities stationed outside the University of Cincinnati Medical Center's Emergency room following a shooting in downtown Cincinnati that left at least four dead, including the gunman, and several injured on September 6, 2018.
"Terrible shooting incident in the heart of our city this morning", City Councilman P.G. Sittenfeld tweeted. "The scourge of gun violence leaves only loss".
Perez's aunt said her nephew held various jobs and was now working, though his aunt and her family did not know where.