Two patrol officers who responded to the shooting were wounded, one of them struck in the head by a bullet in the Monday morning shooting.
Louisville Metro Police Department Deputy Chief Paul Humphrey walked reporters through the footage at a news conference on Tuesday.
One still image from surveillance video showed the shooter holding a gun inside the building, surrounded by broken glass. Police said he set up an ambush position to attack officers as they arrived.
Louisville Mayor Craig Greenberg said it was crucial to release the footage because "transparency is important, even more so in a time of crisis".
Police Chief Jacquelyn Gwinn-Villaroel said at a news conference that bank employee Connor Sturgeon, 25, bought the AR-15 assault-style rifle used in the attack at a local dealership on April 4.
Armed with the rifle, Sturgeon killed his co-workers - including a close friend of Kentucky's governor - while livestreaming the attack before he was killed by police, authorities said. Another eight people were wounded.
"We do know this was targeted. He knew those individuals, of course, because he worked there," Gwinn-Villaroel said, but didn't give an indication of a motive behind the shooting.
Gwinn-Villaroel praised the "heroic actions" of officers who engaged the shooter without hesitation when they arrived.
"They went towards danger in order to save and preserve life," she said.
"They stopped the threat so other lives could be saved. No hesitation, and they did what they were called do to."
Officer Nickolas Wilt, who had graduated from training only 10 days earlier, was still critical but stable on Tuesday after being shot in the head, according to University of Louisville Hospital Chief Medical Officer Jason Smith.
Two of the four wounded still in hospital had injuries that were not life-threatening, Smith said.
The shooting, the 15th mass killing in the United States this year, comes two weeks after a former student killed three children and three adults at a Christian primary school in Nashville, Tennessee, about 260 kilometres south. That state's governor and his wife also had friends killed in that shooting.
Kentucky Governor Andy Beshear said he lost one of his closest friends in the shooting.
"Tommy Elliott helped me build my law career, helped me become governor, gave me advice on being a good dad," said Beshear, his voice shaking with emotion.Â
"He's one of the people I talked to most in the world, and very rarely were we talking about my job. He was an incredible friend."
Also killed in the shooting were Josh Barrick, Jim Tutt, Juliana Farmer and Deana Eckert, police said.
"There are no words to adequately describe the sadness and devastation that our Old National family is experiencing as we grieve the tragic loss of our team members and pray for the recovery of all those who were injured," Old National Bank CEO Jim Ryan said in a statement.
Louisville Mayor Craig Greenberg urged unity as the community processes its grief.
"We're all feeling shaken by this, and scared and angry and a lot of other things too. It's important that we come together as a community to process this tragedy in particular but not just this tragedy because the reality is that we have already lost 40 people to gun violence in Louisville this year," he said.
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