A gunman shot dead three people and wounded two others at an Indiana mall Sunday evening before being fatally shot by a bystander, officials said.

The gunman, described as an adult male, was armed with a "long gun" and appeared to have acted alone, Greenwood Police Department Chief Jim Ison said at a news conference.

Officers responded to reports of shots fired around 6 p.m. local time in the food court at Greenwood Park Mall in Greenwood, a town just south of Indianapolis.

Two people injured in the shooting were hospitalized, Eason said, adding at a second news conference that they were in stable condition.

One man and four women were among the dead, Eason said, without specifying who was among the dead or injured. Greenwood Mayor Mark W. Myers said in a statement that one of the injured, a 12-year-old girl, had "minor injuries."

A motive is not yet known, Ison said, but law enforcement has seen surveillance video of the episode.