(CNN) — When a gunman opened fire on revelers enjoying a night out in Dayton, Ohio, early Sunday, he killed nine people in less than a minute. It was the second mass shooting in the United States in less than 24 hours.
Here's what we know:
How it unfolded
The shooting broke out shortly after 1 a.m. Sunday as a man armed with an assault rifle approached the Ned Peppers bar in the downtown Oregon District, where thousands of people fill bars and nightclubs each weekend.
When someone from Ned Peppers grabbed the barrel of the shooter's long gun, the man picked up a handgun to continue the assault. Police officers on patrol nearby shot and killed the gunman less than a minute after the shooting began.
"I really want to -- think about that minute. ... If we did not have police in the Oregon District and the thousands of people in the Oregon District enjoying their Saturday evening, what we could have had in this city," Mayor Nan Whaley said.
The entire incident unfolded on the street.
The gunman has been identified as Connor Betts, 24, according to local and federal law enforcement sources. The FBI and local law enforcement have served a search warrant at the shooter's family home in Bellbrook, Ohio.
US Sen. Sherrod Brown, D-Ohio, described the suspect as a "young white male," and Dayton police said they will release more information later Sunday.
The shooter was wearing body armor, used a ".223 high-capacity" gun and had additional magazines with him, according to Whaley.
The .223 caliber is used in rifles like the AR-15 assault rifle used in previous mass shootings.
In addition to nine people killed, 27 were injured, according to authorities. They have not been identified.
No officers were injured, Dayton Deputy Director and Assistant Chief of Police Lt. Col. Matt Carper said.
Local, state and federal authorities, including the Bureau of Alcohol, Tobacco, Firearms and Explosives, are investigating the shooting and what led up to it.
The motive is not known.
"We don't know the thoughts of the shooter at this time," Whaley said.
A vigil is planned for 8 p.m. Sunday. Condolences for the city and calls to end gun violence resonated across social media Sunday with the hashtags #DaytonStrong and #EnoughisEnough trending on Twitter.
"God bless the people of El Paso Texas. God bless the people of Dayton, Ohio," he wrote in a tweet.
Brown called on Senate Majority Leader Mitch McConnell to "bring the Senate back tomorrow" to pass a gun-buying background check measure in the wake of the shootings in Dayton and in El Paso.
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