Multiple people have been shot and medics are reporting critical patients in the area of East 5th Street in the Oregon District, local newspaper The Dayton Daily News reports.
"We had officers in the immediate vicinity when this shooting began and were able to respond and put an end to it quickly".
The attack arrived a little over 12 hours after a mass shooting at an El Paso, Texas shopping center killed 20 people and left 26 injured. At least 16 others went to area hospitals with injuries.
Tweets from the Dayton Police Department's official account urged locals to stay indoors and contact them with any information concerning the incident or the shooter.
"This is a large scene and investigation".
A Facebook post suggested a person had taken "the gun from (the shooter)", who is now dead.
Police told the Associated Press that they did not have representatives available to speak to the media.
The shooting reportedly took place inside or near Ned Peppers Bar in the city's Oregon District.
At least nine people have been killed after a gunman targeted an OH bar in the early hours.