Police Chief Richard Biehl says Connor Betts killed his sister and eight others in Dayton, Ohio less than 30 seconds before police fatally shot him, in second US mass shooting in less than 24 hours.

Authorities walk among evidence markers at the scene of a mass shooting, Sunday, August 4, 2019, in Dayton, Ohio.
Authorities walk among evidence markers at the scene of a mass shooting, Sunday, August 4, 2019, in Dayton, Ohio. (AP)

A gunman in body armour opened fire early on Sunday in a popular entertainment district in Dayton, Ohio, killing nine people, including his sister, and wounding dozens of others before he was quickly slain by police, city officials said.

Connor Betts, 24, was killed by police less than a minute after he started shooting a 223-calibre rifle in the streets of Dayton's historic Oregon District about 1 am in the second US mass shooting in less than 24 hours. 

Police haven't released further information about Betts or publicly discussed a motive.

His 22-year-old sister Megan, the youngest of the dead, were all killed in the same area, police said.

The other men and women who were killed ranged in age from 25 to 57.

Dayton Mayor Nan Whaley said the shooter was wearing body armour and had additional high-capacity magazines. Had police not responded so quickly, "hundreds of people in the Oregon District could be dead today," she said.

The neighbourhood, home to bars, restaurants and theatres, is "a safe part of downtown," said police Lt. Col. Matt Carper.

Whaley said at least 27 people were treated for injuries, and at least 15 of those have been released.

Several more remain in serious or critical condition, hospital officials said at a news conference. Some suffered multiple gunshot wounds and others were injured as they fled, the officials said.

TRT World's Natasha Hussain has more.

'Words can't describe it'

Nikita Papillon, 23, was across the street at Newcom's Tavern when the shooting started. She said she saw a girl she had talked to earlier lying outside Ned Peppers Bar.

"She had told me she liked my outfit and thought I was cute, and I told her I liked her outfit and I thought she was cute," Papillon said. She herself had been to Ned Peppers the night before, describing it as the kind of place "where you don't have to worry about someone shooting up the place."

"People my age, we don't think something like this is going to happen," she said. "And when it happens, words can't describe it."

Tianycia Leonard, 28, was in the back, smoking, at Newcom's. She heard "loud thumps" that she initially thought was someone pounding on a dumpster.

"It was so noisy, but then you could tell it was gunshots and there was a lot of rounds," Leonard said.

Staff of an Oregon District bar called Ned Peppers said in a Facebook post that they were left shaken and confused by the shooting.

The bar said a bouncer was treated for shrapnel wounds.

A message seeking further comment was left with staff.

Investigation under way

President Donald Trump was briefed on the shooting and praised law enforcement's speedy response in a tweet on Sunday. 

Trump said that "hate has no place in our country" after two mass shootings that left 29 people dead but also blamed mental illness for the violence.

"We have to get it stopped. This has been going on for years... and years in our country," Trump said in remarks from New Jersey.

Governor Mike DeWine issued his own statement, announcing that he ordered flags in Ohio remain at half-staff and offering assistance to Whaley and prayers for the victims.

Whaley said she has been in touch with the White House, though not Trump directly, and with DeWine. She said more than 50 other mayors also have reached out to her.

The FBI is assisting with the investigation.

A family assistance centre was set up at the Dayton Convention Center, where people seeking information on victims arrived in a steady trickle throughout the morning, many in their Sunday best, others looking bedraggled from a sleepless night. Some local pastors were on hand to offer support, as were comfort dogs.

El Paso shooting

The Ohio shooting came hours after a young man opened fire in a crowded El Paso, Texas, shopping area, leaving 20 dead and more than two dozen wounded. Just days before, on July 28, a 19-year-old shot and killed three people, including two children, at the Gilroy Garlic Festival in Northern California.

Sunday's shooting in Dayton is the 22nd mass killing of 2019 in the US, according to the AP/USA Today/Northeastern University mass murder database that tracks homicides where four or more people were killed — not including the offender. The 20 mass killings in the US in 2019 that preceded this weekend claimed 96 lives.

Whaley said the Oregon District is expected to reopen Sunday afternoon, and a vigil is planned Sunday evening. The minor league Dayton Dragons who play in nearby Fifth Third Field postponed their Sunday afternoon game against the Lake County Captains "due to this morning's tragic event."

The shooting in Dayton comes after the area was heavily damaged when tornadoes swept through western Ohio in late May, destroying or damaging hundreds of homes and businesses.

"Dayton has been through a lot already this year, and I continue to be amazed by the grit and resiliency of our community," Whaley said.

Mexico vows legal action to protect nationals

Mexican Foreign Minister Marcelo Ebrard said Mexico will take legal action to protect Mexicans and Americans of Mexican descent after the shooting in El Paso, Texas.

In a video statement, Ebrard called the shooting an "act of barbarism" and said the country's first priority is attending to the impacted families.

Next, he said, Mexico plans to seek legal measures to protect Mexican nationals and Mexican-Americans in the US.

Mexican officials say three Mexican nationals were killed and another six were wounded in the Saturday shooting at a Texas Wal-Mart.

El Paso is a popular weekend shopping destination for Mexicans who live across the border, in Ciudad Juarez.

The shooter appears to have been targeting Hispanics and authorities are investigating it as a hate crime.

Source: TRTWorld and agencies