Those killed in Dayton were four women and five men and ranged in age from 22 to 57, authorities said.

The 24-year-old gunman who killed nine people in a rampage in Dayton, Ohio, had a troubled past, including threatening fellow students in high school, authorities said, but police said it was too soon to establish a motive for the slaughter.

The gunman, wielding an assault-style rifle and wearing body armor and a mask, inflicted carnage early on Sunday on a neighborhood known for its night life.

Police identified the shooter as Connor Betts, 24, of Bellbrook, Ohio, a Dayton suburb. He was the third young man to take a rifle and go on a public killing spree in the United States within a span of a week, renewing alarm at the national crisis of mass shootings.

The killings in Dayton began at around 1 a.m. on Sunday in the Oregon District and ended rapidly when police who were nearby moved in and shot Betts dead. Those killed included Betts' sister. At least 14 people were wounded by bullets, while others still were injured as they fled. Six of the nine people killed were black.

The gunman shot at least 41 bullets in the seconds before he was killed, Dayton Police Chief Richard Biehl told reporters on Monday. Police officers ended the rampage in about 30 seconds, Biehl said on Sunday.

Investigators were still trying to pin down a motive, Biehl said. Agents from the Federal Bureau of Investigation were helping police.

"We have a lot of evidence still to go through," Biehl said. "Just based on where we're at now, we are not seeing any indication of race being a motive."

Betts had been troubled in high school, at one point drawing up a "hit list" of students he wanted to kill or otherwise harm, authorities said.

He also had a history of threatening women who spurned his advances, CNN reported. News media reported that at one point in high school he was taken off a school bus by police.

Apart from his high school troubles, Betts had been issued tickets for speeding and other minor traffic offenses, police said.

He had been studying psychology at a community college and working at a Chipotle restaurant. In an online profile, Betts reportedly described himself as "Good under pressure. Fast learner. Eager to overachieve."

Nothing in Betts' record precluded him from purchasing the assault-style weapon, which had been modified since it was sold, the police chief said.

The rifle was fitted with an extended drum magazine that could hold 100 rounds. The gun was bought legally online from a dealer in Texas and shipped to a local firearms dealer, police said.

Betts' sister Megan Betts, 22, was one of the first to be killed. Biehl said the siblings had arrived in the same vehicle with a third person earlier in the evening but separated before the rampage.

The companion was wounded in the shooting, police said.

The shooting in Dayton, a riverfront city of about 140,000 people in southwestern Ohio, took place just 13 hours after a mass shooting at a Walmart store in El Paso, Texas, where 20 people were killed and 26 others wounded. The 21-year-old suspect in that shooting was arrested.

"Nightmare" For Parents

U.S. President Donald Trump addressed the spate of shooting sprees from the White House on Monday and called Betts a "twisted monster." He said law enforcement must do more to spot the "early warning signs" of would-be mass murderer.

The two mass shootings reverberated across the U.S. political arena with some Democratic presidential candidates accusing Trump, a Republican, of stoking racial divisions. Trump said on Sunday that "hate has no place in our country."

Those killed in Dayton were four women and five men and ranged in age from 22 to 57, authorities said.

"There isn't much discrimination in the shooting," Assistant Police Chief Matt Carper told reporters. "It happened in a very short period of time."

One of those killed, Nicholas Cumer, was a week shy of completing his internship at Maple Tree Cancer Alliance, a non-profit patient care center in Dayton.

The center said in a statement it had offered Cumer a full-time job last week. "He loved his patients and served them well, with a loving and caring spirit," the statement said. Two of his colleagues were also shot and expected to make a full recovery.

Lois Oglesby, a nursing student with a newborn child and a young daughter, was also killed, the Atlanta Journal-Constitution reported.

Biehl said Betts' parents were having a tough time. "This is a nightmare for them and I think they are struggling as I think you can understand," he said at the news conference.

Four of those injured in the attack remained in serious condition and one person in critical, medical authorities said.

The shootings in Texas and Ohio happened a week after a teenager killed three people with an assault rifle at a food festival in Northern California before taking his own life.