Dayton, Ohio was seconds away from a “catastrophic loss of life”, the city’s police chief said. Nine people were killed and 27 injured by Connor Betts, 24, who opened fire on revellers as they were leaving bars in the Oregon district of the city.
Among those who died was his sister, Megan, 22.
Graphic video footage released by police showed people running for safety as Betts unleashed a volley of bullets.
Many rushed back into the bars they had just left, for safety.
Tianycia Leonard, 28, was in the back, smoking, at Newcom's. She heard "loud thumps" that she initially thought was someone pounding on a skip.
"It was so noisy, but then you could tell it was gunshots and there was a lot of rounds," she said.
The footage showed Betts, who was wearing a bullet-proof vest and was armed with .233 rifle and 100 round drum magazines, trying to get into Ned Peppers bar.
He was shot dead by police within 30 seconds of their being alerted to the threat.
“Had that individual made it through the doorway of Ned Peppers with that level of weaponry there would have been a catastrophic loss of life,” said Dayton’s police chief, Richard Biehl.
President Donald Trump, paid tribute to police for their swift action. “As bad as it was, it could have been so much worse.”
Of the nine people who were killed, six were black, the others were white.
Police declined to speculate on what drove Betts, whose only encounter with police had been for minor motoring offences, to embark on a deadly shooting spree.
Rob Portman, a Republican senator, paid tribute to the police. "Their courage was extraordinary. They saved lives, probably hundreds of lives, given the situation," he said.
"We all saw workers in Hazmat suits who were having to clear away blood off the sidewalk from the tragedy last night."
Mr Portman added: "How could someone point a gun at someone he had never seen or known and pull the trigger."