Mass shootings roil US politics anew

Trump called the El Paso shooting a "hateful act" and "an act of cowardice". He ordered flags at half-staff and said he would speak on the shootings at 10 am Monday in Washington.

Democratic presidential candidate Beto O'Rourke, a former Texas congressman, returned to El Paso after the attack, his hometown.

"Let's be very clear about what is causing this and who the president is," O'Rourke said. "He is an open, avowed racist and is encouraging more racism in this country."

"There's no question that white nationalism is condoned at the highest levels of our government," Democratic candidate Pete Buttigieg, the mayor of South Bend, Indiana, told Fox News Sunday.

Democratic candidate Julian Castro, former mayor of San Antonio, Texas, said on ABC that Trump's "spoken about immigrants as being invaders. He's given license for this toxic brew of white supremacy to fester more and more in this country."

A hallmark of Trump's presidency has been his determination to curb illegal immigration.

Former vice-president Joe Biden, the front-runner for the Democratic nomination, called for an end to "our gun violence epidemic."

"There's no benefit here in trying to make this a political issue; this is a social issue, and we need to address it as that," Acting White House Chief of Staff Mick Mulvaney said Sunday on ABC's This Week.

Police said Crusius opened fire on shoppers, many who were looking for back-to-school supplies, before surrendering to officers outside the store.

A 2,300-word "manifesto", which investigators were working to confirm was posted by Crusius, declares support for a gunman who killed 51 people on March 15 at a mosque and an Islamic center in Christchurch, New Zealand.

"Hispanics will take control of the local and state government of my beloved Texas, changing policy to better suit their needs," the manifesto said.

"From the manifesto that we first saw, we attribute that manifesto directly to him," El Paso Police Chief Greg Allen said Sunday.