A gunman armed with a rifle opened fire in an El Paso shopping area packed with as many as 3,000 people during the busy back-to-school season, leaving 20 dead and more than two dozen injured, police said.
Hours later, there was another mass shooting across the country. Police in Dayton, Ohio, said nine people were killed and at least 16 others wounded by a shooter. He was later shot dead by responding officers.
Authorities are investigating the possibility that the Saturday shooting in El Paso was a hate crime, working to confirm whether a racist, anti-immigrant screed posted online shortly beforehand was written by the man arrested in the attack on the 680,000-resident border city.
Despite initial reports of possible multiple gunmen, the man in custody is believed to be the only shooter, police said. Two law enforcement officials who spoke to The Associated Press on condition of anonymity identified him as 21-year-old Patrick Crusius. Authorities did not release his name at a news conference, but said the gunman was arrested without police firing any shots and is from Allen, which is a nearly 10-hour drive from El Paso.
Many of the victims were shot at a Walmart, according to police, who provided updates about the shooting in English and Spanish in the largely Latino city. The shopping area is about eight kilometres from the main border checkpoint with Ciudad Juárez, Mexico.
"The scene was a horrific one," said El Paso Police Chief Greg Allen, adding that many of the 26 people who were hurt had life-threatening injuries.
The shooting came less than a week after a 19-year-old gunman killed three people and injured 13 others at the popular Gilroy Garlic Festival in California before dying of a self-inflicted gunshot wound.
Adriana Quezada said she was in the women's clothing section of the Walmart in El Paso with her two children when she heard gunfire.
"But I thought they were hits, like roof construction," Quezada, 39, said of the shots.
Her 19-year-old daughter and 16-year-old son threw themselves to the ground, then ran out of the store through an emergency exit. They were not hurt, Quezada said.
Ryan Mielke, a spokesman for University Medical Center of El Paso, said 13 of the injured were taken to the hospital with injuries, including one who died. Two of the injured were children who were transferred to El Paso Children's Hospital, he said.
Eleven other victims ages 35 to 82 were being treated at Del Sol Medical Center, hospital spokesman Victor Guerrero said.
In Dayton, Ohio, police said they intervened to end the violence, leaving the shooter dead.
Assistant Police Chief Matt Carper said the incident began at 1am. local time in Dayton's Oregon District, a downtown historic neighbourhood known for its nightclubs, bars, art galleries and shops.
The motive behind the shooting was not immediately clear and investigators believed the individual had acted alone, Carper said.
Officers who were on patrol in the area reached the scene shortly after the shooting began to confront the shooter, whose identity, age or gender were not immediately disclosed.
"We had officers in the immediate vicinity when this shooting began and were able to respond and to put an end to it quickly," the Dayton Police Department said in a Twitter post.
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