'Many more people would have died': Armed bystander killed gunman who had 3 guns and 100 rounds of ammunition, police say

(CNN) The gunman who killed three people and injured two others at a mall in Greenwood, Indiana, Sunday evening was armed with two rifles, a Glock pistol and more than 100 rounds of ammunition, police said.

The 20-year-old man, identified as Douglas Sapirman, used only an AR 15-style rifle in the shooting, firing off 24 rounds before he was shot and killed by a bystander. Police initially said Sapirman was shot less than two minutes after the attack began, but revised that to 15 seconds on Tuesday, according to Greenwood Police Chief James Ison.

"This error was simply a result of misreading notes during the conference," Ison said in the statement. "I feel the need to correct this immediately."

As Sapirman let off rounds from a restroom area into the mall's food court, Elisjsha Dicken, 22, of Seymour, Indiana, fired 10 shots at Sapirman from his Glock handgun, preventing "many more" deaths, Ison said at a press conference Monday.

"He engaged the gunman from quite a distance with a handgun -- was very proficient in that, very tactically sound and as he moved to close in on the suspect he was also motioning for people to exit behind him," Ison said. "Many more people would have died last night if not for a responsible armed citizen that took action very quickly."