A laptop and can of butane were found inside a heated oven at the Greenwood Park Mall shooting suspect's home. Motive remains unclear, authorities say.

• Three people were killed in a shooting at a mall in Greenwood, Indiana, on Sunday evening.
• The shooting suspect was killed by a 22-year-old armed civilian minutes after the first shots were fired.

Authorities investigating a mass shooting at a mall in Greenwood, Indiana, on Sunday evening that left three dead said at a Monday press conference that they are still not clear on the suspect's motive — but they revealed he attempted to destroy a laptop and phone.

The suspect, who was identified as 20-year-old Jonathan Douglas Sapirman of Greenwood, tried to destroy a laptop in a heated oven at his apartment that also contained a can of butane, Chief James Ison of the Greenwood Police Department said on Monday. Authorities also found the suspect's cellphone submerged in the toilet.

Ison said at a press conference that he did not want to speculate what the suspect's intentions were, but that authorities are currently trying to retrieve as much data as possible from the damaged electronics.

The shooter's motives were not clear as of Monday.

Three people were killed in the shooting at Greenwood Park Mall before the shooter was killed by an armed civilian.

Authorities traced a timeline of the incident through surveillance footage.

Around 4:54 p.m., the suspect entered the food court bathroom, where he waited one hour and two minutes before carrying out the shooting.

It was the most "puzzling" aspect of the incident, Ison said, but officials believe that is where the suspect prepared for the attack.

The suspect killed three people and injured two others, including a 12-year-old girl who was hit by a "bullet fragment" most likely from a ricochet, Ison said. The girl suffered minor wounds.

The deceased were identified as a couple from Indianapolis — Pedro Pineda, 56, and Rosa Mirian Rivera de Pineda, 37 — and Victor Gomez, 30, of Indianapolis.

The shooting lasted a few minutes and the suspect shot 24 rounds, Ison said.

The gunman was then confronted by a 22-year-old armed civilian who was shopping with his girlfriend at the time, authorities said. The civilian had a handgun and shot about 10 rounds, fatally injuring the shooter.

Authorities identified the civilian as Elisjsha Dicken of Seymour, Indiana, and hailed him as a "good Samaritan."

"His actions were nothing short of heroic," Ison said, adding that Dicken did not have a military background or police training.

Not much is known about the suspect

According to Ison, the suspect had a juvenile record for minor offenses, including a fight at school and for being a "juvenile runaway."

The suspect was in possession of two weapons, multiple magazines, and more than a hundred rounds of ammunition. Ison said the suspect did not have a permit but was legally allowed to carry under Indiana state law.

Indiana removed its permit required to purchase and carry a handgun in public in March, according to Indianapolis Star.

Authorities said that the suspect had been practicing shooting at a local shooting range, based on interviews with family members.

Family members also told officials that the suspect resigned from a warehouse job in May and could have received an eviction notice from his apartment where he lived alone and is near the mall. Authorities have submitted a subpoena for his rental records.

Ison added that family members were surprised that the suspect was capable of the act of violence.

"They said there were no indicators that he was violent or unstable," Ison said.