Three people are dead and two others injured after a shooter opened fire in the food court of a Greenwood, Indiana, shopping mall Sunday evening, police say. Around 6:00 p.m. local time, multiple people called 911 to report an active shooter at the Greenwood Park Mall, Greenwood Police Department Chief Jim Ison told reporters. Investigators believe the unidentified gunman, an adult man, was shot and killed by a lawfully armed 22-year-old man who "observed the shooting in progress," Ison said. The victims include one male and four females, including a 12-year-old girl whose parents brought her to the hospital with minor injuries after the shooting, the chief said, noting she is expected to be "just fine." The second injured victim was hospitalized and in stable condition as of Sunday evening, Ison said. Olivia Harding said she was at the Old Navy in the mall when she and her mom heard four gunshots and thought the nearby carousel was breaking down. "Next thing you know, you hear about six more shots and you see everybody running," Harding told CNN affiliate WISH. Harding said she doesn't think she'll come back to a mall "for a very long time." The gunman appears to have used a long-gun rifle, according to Ison, though law enforcement had not recovered any weapons from the scene at the time he was speaking to reporters, he said. There have been 350 mass shootings this year, according to Gun Violence Archive which, like CNN, defines a mass shooting as one in which four or more people are shot, not including the shooter. The local community now joins a slew of others also grappling with the aftermath of mass shootings, including communities reeling from recent massacres at an elementary school in Uvalde, Texas, and a July Fourth parade in Highland Park, Illinois. SWAT teams have cleared the mall and determined there are no additional threats in the building, Ison said, noting that investigators are now processing the crime scene. Police are still investigating the shooter's motive and questioning people who were inside the mall at the time of the attack, police said. They are asking all witnesses to contact authorities and have requested that the public stay away from the mall at this time. "This tragedy hits at the core of our community," Greenwood Mayor Mark Meyers said in a Facebook post. "Please offer your prayers to the victims and our first responders." Meyers also expressed his thanks to the person who fatally shot the gunman while the shooting was in progress. "This person saved lives tonight. On behalf of the City of Greenwood, I am grateful for his quick action and heroism in this situation," the mayor said in another statement later Sunday evening. Multiple agencies responded to the scene and are assisting in the incident, including the FBI, ATF, Johnson County Sheriff's Department and Department of Homeland Security, Ison said. Ison said the Greenwood Police Department has trained for a mass shooting scenario and has performed "multiple mall exercises" to prepare for active shooter situations. "But I'm going to tell you, the real hero of the day is the citizen that was lawfully carrying a firearm in that food court and was able to stop this shooter almost as soon as he began," Ison said. — CNN