Updated at 10:50 a.m. ET

In the second major mass shooting in less than 24 hours in the United States, officials say a gunman killed nine people and injured 27 early Sunday in Dayton, Ohio.

The shooter was killed by police officers.

On Saturday, a gunman killed 20 people and injured 26 at an El Paso, Texas, Walmart.

“As a mayor, this is a day that we all dread happening,” Dayton Mayor Nan Whaley told reporters Sunday morning.

“It is a terrible day for Dayton but I am so grateful for Dayton police’s fast action,” she said, adding that hundreds of people could have been killed based on the size of crowds in the area on a Saturday night.

Twenty-seven people are in multiple hospitals across the city, some with life-threatening injuries, she said.

Police were already on patrol in the area full of nightclubs known as the Oregon District and stopped the shooter in less than one minute, the mayor said.

Details about the condition of some of the victims emerged at a press conference Sunday morning. Dr. Greg Semon of Miami Valley Hospital said at least one person is in critical condition and four others are being treated by trauma and other specialists.

He added, “They are obviously doing everything they can to maximize their outcomes.”

Sixteen of the victims received by the hospital were treated for gunshot wounds. Others arrived with wounds and injuries caused by “an effort to escape the shooter,” Semon said.

An official from Kettering Health Network said victims were taken to three of its hospitals. Four people are in serious condition.

Earlier on, Lt. Col. Matt Carper of the Dayton Police Department had said Dayton is “a very safe area.” “This is extremely unusual obviously for any community, let alone Dayton. And in our Oregon District, this is unheard of and very sad. It’s a very tragic evening,” he told reporters shortly after 4 a.m. Sunday.

Police say the shooting started at 1 a.m. outside. In what Carper called a “very short timeline of violence,” the shooter used what police called a “long gun.” Whaley later said the shooter wore body armor and used a .223 caliber weapon with a high-capacity magazine and had additional magazines.

Carper said police were investigating the possibility of more shooters being involved, but “it looks like” only one shooter was responsible.

He said they’ve identified the suspect. No name has been released.

“We understand that the public wants to know who this person is. We are working very hard to give the public an answer as to what the motivation might have been for this attack,” he said.

No police officers were injured.

The Dayton police have trained for years for active shooting situations, Carper said. Twenty-one medic units responded to the scene and the FBI is on the scene to assist in the investigation.

This is a developing story. Some things that get reported by the media will later turn out to be wrong. We will focus on reports from police officials and other authorities, credible news outlets and reporters who are at the scene. We will update as the situation develops.

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