A gunman wearing body armor and carrying extra magazines carried out his carnage in less than a minute, killing nine people and wounding dozens more at an entertainment district in Dayton, Ohio — the second US mass shooting in 13 hours, officials said Sunday.

Police responded in less than a minute to the shooting shortly after 1 a.m. Sunday, said Dayton Mayor Nan Whaley, in the Oregon District, which contains a number of restaurants, bars and theaters.

She said if the police hadn’t responded so quickly, the death toll could have been much higher​ because thousands of people were on the streets.​

“The officers were there less than a minute from the beginning of the shooting. The shooter was able to kill nine people and injure 26 in less than a minute,” ​Whaley said during a news conference​ Sunday.​

She said​ the gunman, who has not been identified, wore body armor and used a “.223 high-capacity” rifle and carried extra magazines.​

​Lt. Col. Matt Carper of the Dayton Police Department said officers were nearby when the shooting started and “neutralized the shooter” in less than one minute. ​

It also appears the shooter acted alone and officials are still seeking a motive for his attack.

The mass shooting took place hours after a 21-year-old Texas man walked into a Walmart in the border town of El Paso, Texas, and opened fire, killing 20 and injuring 26 people.

The suspect, identified as Patrick Crusius, of Allen, a suburb outside Dallas, posted a hate-filled rant against immigrants and Hispanics online just before the shooting.

Police captured him several minutes after the shooting stopped.

In Dayton, witnesses described how the mayhem unfolded after the gunman opened fire at Ned Peppers, a pub in the Oregon District.

“The screams, the cruisers, the chaos, I have never been pushed out of Newcomb’s but the security guards were running around telling people to get out,” Nikita Pappillion ​told WLTW in Cincinnati.

“Just how everybody was acting you knew something was wrong. When you came outside as soon as you get to front street you see the bodies and you knew that this was different, and you knew it was something that you never thought of experiencing never experienced, wouldn’t want anyone to experience​,​”​ the 23-year-old said.

With Post Wires ​