A gunman shot and killed three people and injured two others at a mall in Indiana on Sunday evening before he was fatally shot by a bystander, officials said.

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

Officers responded to reports of shots fired about 6 p.m. local time at the food court in Greenwood Park Mall in Greenwood, a city just south of Indianapolis. The two people wounded by the gunfire were hospitalized, Ison said, adding at a second news conference that they were in stable condition.

The victims included one male and four females, Ison said, without specifying which were among the dead or injured. Greenwood Mayor Mark Myers said in a statement that one of the injured was a 12-year-old girl with "minor injuries."

A motive was not yet known, Ison said, but law enforcement had viewed surveillance video of the episode.

A nearby "good Samaritan" shot the gunman, Ison said. He added that the bystander "appears to be cooperating fully."

"The real hero of the day is the citizen who was lawfully carrying a firearm in that food court and was able to stop the shooter almost as soon as he began," Ison said. He said he believed the bystander had a handgun.

"We experienced a mass shooting this evening," Myers said in a statement, adding that there was "no further threat."

Myers said in a second statement that while the gunman's identity and motive were not yet known, "we do know that someone we are calling the 'Good Samaritan' was able to shoot the assailant and stop further bloodshed. This person saved lives tonight."

Indiana Gov. Eric Holcomb, R, said in a statement that he was "monitoring the ongoing investigation" and that state police were assisting local law enforcement.

Lawmakers in states across the country are seeking to pass legislation expanding or restricting gun access in the aftermath of mass shootings in Buffalo and Uvalde, Texas. Indiana's new handgun law, which took effect July 1, lifted the permit requirement to carry, conceal or transport a handgun in the state.

Indiana still has some restrictions on who can possess a handgun. For certain groups - including people who have committed felonies and those under the age of 18 - it is still illegal to carry a handgun.

To buy a long gun in Indiana, a person must be 18 or older and present a valid ID. The state does not explicitly require those purchasing a long gun to submit to a background check, but it is required by federal law.