Twenty people were killed and more than two dozen injured in a shooting Saturday in a busy shopping area in the Texas border town of El Paso, the state’s governor said.

Among the possibilities being investigated is whether it was a hate crime, the police chief said. Two law enforcement officials who spoke to The Associated Press on condition of anonymity identified the suspect taken into custody as 21-year-old Patrick Crusius. El Paso police haven’t released his name, but confirmed the gunman is from Allen near Dallas.

Police said another 26 people were injured and most were being treated at hospitals. Most of the victims were believed to have been shot at a Walmart near the Cielo Vista Mall, they said, adding that the store was packed with as many as 3,000 people during the busy back-to-school shopping season.

“The scene was a horrific one,” said El Paso Police Chief Greg Allen, who described many of those hurt as having life-threatening injuries. He also said police found a post online that may have been written by the suspect — one reason authorities are looking at whether it was a hate crime.

El Paso, which has about 680,000 residents, is in West Texas and sits across the border from Juarez, Mexico.