Gunfire erupted about half an hour before bars were to close at 3am in a neighbourhood popular with university students and other young people.
Indianapolis police chief Rick Hite said: "It looks like it was two guys who bumped into each other and it took off from there. There was no rhyme or reason."
Police arrested a 23-year-old man on a preliminary charge of being a felon in possession of a firearm and questioned him about the shooting. He was not charged in connection with the shooting, police spokesman Lt Chris Bailey said.
Police said one man was in critical condition at a local hospital. Five other men and a woman also were shot but did not have life-threatening injuries.