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