Police said that the situation was under control shortly before 10:00am ET, but they are still investigating.
Police believe Perez shot five victims during the attack. Three died and two others survived and are hospitalized, including a Louisville woman. Perez was armed with a 9 mm gun and Isaac estimated he had about 200 rounds of ammunition.
"This is clearly an act of grotesque violence to innocent people and it should frighten all of us", said Cincinnati Mayor John Cranley.
Police earlier characterized it as an "active shooter/officer involved shooting incident" in a tweet, but did not elaborate.
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Cincinnati police chief Eliot Isaac called the rampage "very horrific", though police said the circumstances surrounding the violence and a potential motive are thus far elusive. The shooting took place at the corporate headquarters, a skyscraper on Cincinnati's main downtown square.
Cranley a year ago joined more than 1,000 mayors across the country in signing a pact to end illegal gun use and enforce current gun laws.
"We prepare for situations like these and hope they never happen", said Amanda Nageleisen, UC Health spokeswoman. Our Country is the only first-world nation with this level of mass shootings.
Federal and state agents were also on the scene as investigators swept the building.
One victim was identified as 64-year-old Richard Newcomer, a superintendent with the Gilbane Building Company, a construction company based in Cincinnati.
Radio traffic indicated other victims may have been transported to Good Samaritan Hospital. Two of those patients are among the dead, officials said, one is in serious condition and the other in critical condition.
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Witnesses told local media they heard as many as 20 gunshots.
"I heard about eight gunshots, and I actually got on my knees".
"Everybody was in there crying". "We just saw glass and everything flying". "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. "After that, I started running", Richardson said.
He did not hear the shots, he said, but he saw emergency responders wheeling out victims on stretchers.
Carla Herreria contributed reporting. We have more details here.
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