Nine people have been killed and at least 27 injured in a mass shooting in Dayton, Ohio - the second in the US in 24 hours.
Police confirmed they killed the gunman at the scene within a minute of him opening fire.
The shooting began at 01:07 local time (05:07 GMT) in the Oregon district of the city centre.
The local mayor said the gunman wore body armour and came carrying extra ammunition.
The suspect used a .223-calibre assault rifle with high-capacity magazines.
Nan Whaley told reporters she was "amazed" by the quick response of the officers which she said prevented further deaths, but also stressed it would be a "very, very difficult time" for families of victims.
"As a mayor, this is a day that we all dread happening," she said. "What's very sad is I've got messages from mayors across the country - it's sad that we've all gone through it."
The incident came only hours after a mass shooting in El Paso, Texas which left at least 20 people dead.
The Gun Violence Archive, which categorises mass shootings as four or more people shot or killed, says there have been 251 so far this year.
What happened in Dayton?
Footage posted on social media showed people running as dozens of gunshots echoed through the streets.
It is thought the shooting took place outside Ned Peppers Bar on E 5th Street. The bar later posted on social media its staff were safe.
Police said all the fatalities happened outside in the street.
Jae Williams told the BBC he was at a nearby rap performance when they were told to evacuate.
"I was very shocked," he said. "We all evacuated quickly and safely. We were told to avoid the Oregon district."
"I got to my car, I could see cops, multiple ambulances."
Another eyewitness told Reuters they had been in a nearby nightclub, Newcom's, when the shooting happened. "The screams, the cruisers, the chaos... the security guards and themselves were running around and telling people to get out and just how everybody was acting, you knew something was wrong," she said.
"And then when you came outside, as soon as you hit the front street, you've seen the bodies, you knew this was different. You knew it was something that you never thought of experiencing, never experienced, wouldn't want anyone to experience."
Assistant Police Chief Matt Carper told reporters that officers managed to take down the gunman.
"Our people are very well trained for a situation like this," he said, adding it was "very fortunate that the officers were in close proximity".
Nearby hospitals had received 27 people and discharged 15 by 10:00 local time (14:00 GMT).
Who was the attacker?
Law enforcement sources told CBS News the gunman was 24-year-old Connor Betts from Bellbrook, Ohio.
Police were searching his house on Sunday, the news network said.
Officially, however, few details have been released and there is no indication yet of any motive. Police said they had identified the attacker, but declined to identify him at a news conference.
Mayor Whaley said he was wearing body armour and was carrying extra magazines for his weapon.
"We don't know the thoughts of the shooter," she said.
Officer Carper, who stood beside Mayor Whaley, said it was "very early in the investigative stages" and could not confirm there was only one gunman involved, but said so far that looked likely.
FBI agents are also assisting police with the investigation.
What's been the reaction?
At a series of news conferences, Mayor Whaley asked people to think of those people "who went downtown on a Saturday night and thought they'd be safe".
She said that the Oregon district was "one of the safest places in the whole region".
"Frankly, we're at a situation now in our country that these are so random," she said.
She also said the city had gone through a "a really tough year", drawing a comparison to a series of 14 tornadoes that hit Dayton in March.
"What really goes through my mind is one seems completely preventable," she said. "I just question when is enough, enough."
She earlier tweeted that she was "heartbroken" after the shooting, and thanked first responders.
I’m heartbroken. Thank you to our first responders for all that you’ve done. We will share updates as we have more information.— Nan Whaley (@nanwhaley) August 4, 2019
On Twitter, singer Lizzo called on people not to "normalise" shootings, saying that her family in Dayton were safe "but that's not the case for nine other families".
Just got off the phone w/ fam in Dayton... it was a close call for them but that’s not the case for 9 other families— |L I Z Z O| (@lizzo) August 4, 2019
between this & the terrorist attack in El Paso & recent other shootings I feel completely helpless.. make noise & bring awareness.. vote.. don’t normalize this