The shooting happened in the state capital Columbus at about 16:45 local time (20:45 GMT) on Tuesday, the Columbus Dispatch newspaper reported.
Columbus police later produced body cam footage of the incident, showing several people attacking a person before the girl was shot several times. An inquiry is under way, with officials urging local residents to remain calm.
“This afternoon a young woman tragically lost her life. We do not know all of the details,” Columbus Mayor Andrew Ginther tweeted.
“We will share information that we can as soon as it becomes available,” he added.
An angry crowd later gathered at the scene, US media reported.
The shooting in Columbus happened shortly before a jury found a former police officer guilty of murder over the death of African-American George Floyd on a Minneapolis street last year.
Derek Chauvin, 45, was filmed kneeling on Mr Floyd’s neck for more than nine minutes during his arrest last May.The widely watched footage sparked worldwide protests against racism and excessive use of force by police.