GREENWOOD, Ind. — In a matter of 15 seconds, a mass shooter opened fire at the Greenwood Park Mall, killing three people and injuring two others, before he was shot and killed by a bystander.

One by one, panic-filled 911 calls flooded the Johnson County and Bartholomew County dispatch centers from people who were there during the shooting and ran away, people still hiding inside, and family members of loved ones that were at the mall.

Nearly two hours away, Major Matt Rhinehart was out to dinner with his family when he received a call, alerting him that the Johnson County Bomb Squad was needed at the Greenwood Park Mall for a backpack that had reportedly been found. Normally, this would be what is considered a ‘basic run’ for the team of bomb technicians that work within the county, but in this case, it was quite the opposite.

Rhinehart, who serves as the commander for the county’s bomb squad, said he immediately received another call from the head of the IMPD Bomb Squad, offering whatever help they might need, and informing him this was in response to an alleged active shooter situation.

The two teams are among 12 hazardous devices units in the state, explained Rhinehart. The Johnson County Bomb Squad is made up of four certified bomb technicians and several assistants.

“We all come together and we’re all training the same, so we know the work and we all do it together as one,” Rhinehart said. “It wasn’t IMPD’s jurisdiction with them not being in Johnson County but they’re there to go in and do things with me, and for me and my guys, and my team.”

As bomb technicians with IMPD, Indiana State Police, and federal agencies including the FBI and ATF responded to the mall, Rhinehart knew time wasn’t something he could afford to play with.

“I didn’t even say too much to the family that was there, and I ran out the door,” said Rhinehart.

He left in shorts, a tee-shirt, and sandals and it’s exactly how he looked when arrived on scene, right around the exact time that the bomb technicians were given command of the scene to go in and clear it of any potential explosive hazards.

When asked about his choice to skip the 10 minutes it would have taken to go home and change into his uniform, Rhinehart told FOX59, “I chose to go to be the leader of our bomb squad. Instead of trying to look the part, just be the part.”

In released 911 audio and radio transmissions, an officer could be heard saying, “Who is in the food court that can escort EOD to the package?”

“The officers go in and clear everything to get the medics in and at a certain point it was, I’ll say, obvious what they were dealing with,” said Rhinehart. “When they located the shooter, they knew that this is where he came from. They’re going in looking for more victims, possibly being able to render aid if they had to, and in that time they locate what they believe to be articles he brought in.”

Regardless of whether the articles belonged to the alleged shooter, another mall-goer, posed a potential hazard or not, Rhinehart said the items raised a red flag and someone knew to call for backup.

“Someone came upon something that they believed to be his and they knew not to mess with it,” said Rhinehart.

He said they also had to consider everything, including things like whether the suspect could have come in at any other point during the day, including from a different entrance, or had other items he left behind.

“There are unfortunately people out there that want to do us harm as well as themselves doing the harm. They want to hurt people and they want to hurt us because we’re trying to stop them from hurting people,” Rhinehart explained.

Rhinehart said he went into the scene and worked with the group of bomb technicians from various agencies to clear the scene and ensure there were no further threats to officers, mall staff, or civilians.

“The area that we were responsible for clearing was maybe three rooms,” said Rhinehart, whose team understood how crucial their task was. “We know this is where the investigation is either going to start or end.”

He explained, they have to treat everything as hazardous until they can confidently say they don’t believe it is.

“There’s kind of a saying that goes around on our team, it is until it’s not,” Rhinehart shared.

“We also know that what we do is a big asset to letting everyone else complete their parts at the job,” said Rhinehart. “There’s a lot of weight on our shoulders. You can look, and look, and look, and clear things and make sure this isn’t bad, this isn’t bad, but at a certain point we have to say okay, everyone else can do their job.”

“We don’t get second chances if we miss something.”

An example of why it is so crucial to be thorough and know what to look for that comes to mind is the Columbine High School massacre on April 20, 1999. It’s also why Rhinehart said they train extensively for a wide-variety of situations.

“If someone would’ve went in and missed these devices who knows if it would’ve hurt someone else. More than likely it could have,” said Rhinehart.

There were no explosive devices or hazardous items found at the scene of the Greenwood mass shooting, however, investigators announced during a press conference Monday that a backpack belonging to the accused shooter was found in the bathroom, with ammunition and a broken-down rifle inside.

Rhinehart said in the moments when his team responded and went inside, they knew they had a job to do and despite what they were walking into, they needed to focus on making sure there was no more harm or loss of life due to any potential hazards inside.

“Just the fact of dozens of people getting up and leaving an area and the things that are there for that, it’s overwhelming to the senses just of the sheer mass of everything that’s there,” said Rhinehart. “Notwithstanding the trauma that’s still there, that’s left behind.”

“In my position as far as bomb technician and supervisor of bomb technicians, we have to kind of put that stuff to the side. There’s things that are there that you don’t want to have to think about because we’ve got a job at hand,” said Rhinehart.

He said, their team goes into a situation like this already having the worst-case scenario going through their head.

“There’s nothing that can prepare you for what we saw inside,” said Rhinehart. “Only thing we could do was mentally try and put together what could be.”

The bomb squad also assisted authorities in clearing the alleged gunman’s apartment early Monday morning of any potential explosives. On scene, investigators found a can of butane and a laptop in a hot oven, they confirmed during a press conference earlier this week.

Rhinehart said in light of the tragedy that unfolded, there was no hesitancy from anyone who had the ability to step in and offer help in any way they could.

In addition to the Johnson County Sheriff’s Office, Greenwood Police Department and Fire Department, Rhinehart was told officers from in and out-of-county, including those on and off-duty, Indiana DNR Conservation Officers, and more, rushed to the mall the moment they heard the call come out over the radio.

“What I think gets lost is, the behind the scenes, the personal side of things. You are dropping what you are doing, quite literally, where you go to something that you may have no idea what you’re getting ready to get into,” said Rhinehart. “That’s something that you hope people that don’t do these jobs have to ever see.”