DAYTON, Ohio (AP) - A gunman in body armor opened fire early Sunday in a popular entertainment district in Dayton, Ohio, killing nine people, including his sister, and wounded 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-caliber rifle in the streets of Dayton's historic Oregon District about 1 a.m. in the second U.S. 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 armor 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 neighborhood, home to bars, restaurants and theaters, 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.

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.

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

Gov. 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 center 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.

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 injured. 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 U.S., 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 U.S. 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.

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This story has been corrected to say the shooting took place around 1 a.m., not 1:22 a.m., per a police update.

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Associated Press writers Julie Carr Smyth in Dayton, Michael Balsamo in Orlando, Fla., and Kantele Franko in Columbus contributed.

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