DAYTON, Ohio — The shooter who killed nine people and injured dozens when he opened fire early Sunday in a popular nightlife area of Dayton, Ohio, before being quickly killed by police was a 24-year-old man named Connor Betts, a law enforcement official said. Authorities recently announced his sister was one of the nine victims.

Betts was killed by police less than a minute after he opened fire with a .223-caliber rifle in the streets of the Oregon District around 1 a.m. Sunday in the second U.S. mass shooting in less than 24 hours. Police say his 22-year-old sister, Megan, was the youngest of the deceased victims, who were all killed in the same area. The others were adults ranging in age from 25 to 57.

The official who identified the gunman spoke to The Associated Press on condition of anonymity and was not authorized to discuss an ongoing investigation publicly.

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.

On Sunday, high school classmates of Connor Betts said he was suspended in school for compiling a “hit list” of those he wanted to kill and a “rape list” of girls he wanted to sexually assault.

The accounts by two former classmates emerged after police said there was nothing in the background of Betts that would have prevented him from purchasing the .223-caliber rifle with extended ammunition magazines that he used to open fire.

Both former classmates told The Associated Press that Betts was suspended during their junior year at suburban Bellbrook High School after a hit list was found scrawled in a school bathroom. That followed an earlier suspension after Betts came to school with a list of female students he wanted to sexually assault, according to the two classmates, a man and a woman who are both now 24 and spoke on condition of anonymity out of concern they might face harassment.

“There was a kill list and a rape list, and my name was on the rape list,” said the female classmate.

A former cheerleader, the woman said she didn’t really know Betts and was surprised when a police officer called her cellphone during her freshman year to tell her that her name was included on a list of potential targets.

“The officer said he wouldn’t be at school for a while,” she said. “But after some time passed he was back, walking the halls. They didn’t give us any warning that he was returning to school.”

Bellbrook-Sugarcreek Schools officials declined to comment on those accounts, only confirming that Betts attended schools in the district.

The discovery of the hit list early in 2012 sparked a police investigation, and roughly one-third of Bellbrook students skipped school out of fear, according to an article in the Dayton Daily News.

It’s not clear what became of that investigation. Chief Michael Brown in Sugarcreek Township, which has jurisdiction over the Bellbrook school, did not return calls Sunday about whether his agency investigated the hit list.

Though Betts, who was 17 at the time, was not named publicly by authorities at the time as the author of the list, the former classmates said it was common knowledge within the school he was the one suspended over the incident.

Early Sunday, Betts targeted a historic neighborhood that police Lt. Col. Matt Carper described as “a safe part of downtown.” It is home to bars, restaurants and theaters.

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, local hospital officials said at a news conference.

They said some people suffered multiple gunshot wounds, and others were injured as they fled.

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.

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