CNN — It took just one minute for a gunman to complete his deadly rampage at a Louisville bank before he stopped shooting and waited for police to arrive, according to footage of the massacre described by a city official to CNN.

Connor Sturgeon, a 25-year-old employee poised to get fired from Old National Bank, livestreamed his gruesome attack Monday on Instagram, officials said.

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The video has been removed from the site as investigators comb the footage to try to understand what led up to the mass shooting that left five people dead and several more wounded, including a police officer who was shot in the head.

The footage begins with the clearly visible AR-15-style weapon before a worker inside the bank says good morning to the gunman, the official said.

“You need to get out of here,” the shooter is heard saying to the woman on the livestream, which was taken down by parent company Meta.

The gunman then tries to shoot her in the back but can’t because the safety is on and the weapon still needs to be loaded, the official said. Once the shooter loads the weapon properly and takes the safety off, he shoots the worker in the back, the official said. Her condition is not known.

The shooter then continues his rampage, firing at workers while they tried to outrun him, the official said. The shooter does not go to other populated floors of the bank, the official said.

Once the shooter is done firing, he sits down in the lobby area that looks out onto East Main Street and appears to wait for police, the official said.

The gunman waits about a minute and a half before police arrive – a swift response praised by local leaders – and engage the shooter in a gun battle, the official said.

The gunman was struck and killed.

The death toll increases

The massacre “happened very quickly” in the Old National Bank conference room, said bank manager Rebecca Buchheit-Sims, who attended the staff meeting virtually and watched in horror as gunfire exploded on her computer screen.

“I witnessed people being murdered,” she told CNN. “I don’t know how else to say that.”

Those killed were Joshua Barrick, 40; Juliana Farmer, 45; Tommy Elliott, 63; and James Tutt, 64, police said. Deana Eckert, 57, died later Monday.

The assailant had interned at the bank for three summers and been employed there full-time for close to two years, his LinkedIn profile showed. Sturgeon had been notified he was going to be fired from his job at the bank, the law enforcement source said.

The gunman left a note for his parents and a friend indicating he planned to carry out a shooting at his workplace, the source said, though it is unclear when the message was found.

Sturgeon was still firing when officers arrived, police officials said. At least two were injured, including a rookie who was shot in the head and hospitalized in critical condition.

The gun used in the shooting was an AR-15-style rifle, a federal law enforcement source told CNN. The AR-15 and its offshoots have been the weapon of choice in many of the most horrific mass shootings in recent memory, including the Covenant school shooting in Nashville just two weeks ago that’s reignited a fierce political fight over gun control.

The semi-automatic rifle is the most popular sporting rifle in the US, and 30% of gun owners reported having owned an AR-15 or similar-style rifle, according to the 2021 National Firearms Survey.

Monday’s massacre was the 146th mass shooting so far this year with four or more victims, not including a gunman, according to the Gun Violence Archive.

Kentucky Gov. Andy Beshear ordered flags across the state to fly at half-staff until Friday evening to honor the Louisville victims, but some Democratic lawmakers shared concern the expressions of grief will come and go without meaningful gun violence solutions.

“My worry is that everybody will raise their fists in anger and mourn and then in six weeks, eight weeks we go back to doing the same – nothing,” state Sen. David Yates told CNN on Monday. “I hope that they all don’t have to die in vain like so many of the other victims of these mass shootings. Maybe something positive can come from it.”

President Joe Biden echoed his repeated push for gun reform legislation and called on Republican lawmakers to join Democrats to take action.

“Too many Americans are paying for the price of inaction with their lives. When will Republicans in Congress act to protect our communities?,” the president tweeted.

How the massacre unfolded

The shooting began around 8:30 a.m., police said, about 30 minutes before the bank opens to the public. Bank staff were holding their morning meeting in a conference room when the shooter opened fire, said Buchheit-Sims, the bank manager.

One bank employee frantically called her husband as she sheltered inside a locked vault, her spouse Caleb Goodlett told CNN affiiliate WLKY. By the time he called 911, police already knew about the shooting, he said.

“Just a very traumatic phone call to get,” Goodlett told the affiliate. His wife was not seriously hurt, he said.

Nickolas Wilt, a 26-year-old rookie officer, ran toward the gunfire and was shot in the head, interim Louisville Metro Police Chief Jacquelyn Gwinn-Villaroel said. He had graduated from the police academy just 10 days before the shooting.

Wilt underwent brain surgery and was in critical but stable condition as of Monday afternoon, the chief said.

The bank sits on the fringe of Louisville’s developing downtown business district, said state Sen. Gerald Neal, who represents the district where the shooting happened.

“You wouldn’t really expect anything to happen at this location,” he said.

Despite the shock of the shooting in Kentucky’s most populated city, Neal thinks discussions about gun control in the state will still be an “uphill battle,” he said.

“This is not a state that’s friendly to those who would think about gun reform … or gun control in some way or even reasonable, as you might consider, gun steps that we could take in terms of restricting them. This is not that state. However, the effort continues.”

Victim was an ‘incredible friend’ and mentor

One of the slain victims, bank senior vice president Tommy Elliott, was remembered by local and state leaders as a close mentor and beloved community leader.

“Tommy was a great man. He cared about finding good people and putting them in positions to do great things. He embraced me when I was very young and interested in politics,” Yates, the state senator, told CNN. “He was about lifting people up, building them up.”

Elliott was also close friends with Beshear and Louisville Mayor Craig Greenberg, who said he spent Monday morning at the hospital with Elliott’s wife.

“It is painful, painful for all of the families I know,” Greenberg said. “It just hits home in a unique way when you know one of the victims so well.”

Beshear remembered Elliott as an “incredible friend” and also called the others who were killed “amazing people” who will be missed and mourned by their communities.

The city is setting up a family assistance center in collaboration with the American Red Cross to provide support for those impacted, Greenberg said.

“To the survivors and the families, our entire city is here to wrap our arms around you,” Greenberg added.

Members of the Old National Bank executive team, including CEO Jim Ryan, were in Louisville on Monday after the shooting, the company said on Facebook.

“As we await more details, we are deploying employee assistance support and keeping everyone affected by this tragedy in our thoughts and prayers,” Ryan said in a statement Monday morning.

Gunman had worked at bank for years

Before Monday’s shooting, the gunman had not had “any prior engagement” with police, the interim chief said.

He graduated in December 2020 from the University of Alabama, where he earned his bachelors degree and a masters degree in finance, according to a spokesperson for the university.

After three consecutive summers interning at Old National Bank, he was hired as a Commercial Development Professional in June 2021, according to his LinkedIn profile.

One of Sturgeon’s former high school classmates who knew the shooter and his family well said the horrific news Monday came as a “total shock.”

“I can’t believe it,” said the former classmate, who asked not to be identified and has not spoken with Sturgeon in recent years. “I can’t even say how much this doesn’t make sense.”

CORRECTION: A previous version of this story misspelled Tommy Elliott’s last name.

CNN’s Artemis Moshtaghian, Celina Tebor, Caroll Alvarado, Kristina Sgueglia, Sara Smart and Eric Levenson contributed to this report.