Democratic presidential hopeful Pete Buttigieg on Sunday called on President Donald Trump to condemn white nationalism following a mass shooting that left 20 people dead and more than two dozen wounded.

According to various reports, the shooting took place around 10 a.m. on Saturday at a Walmart near Cielo Vista Mall in El Paso, Texas.

Police said that they have one suspect, a 21-year-old man from Dallas, in custody. He reportedly wrote a 4-page manifesto that includes anti-immigrant statements. El Paso is on the border with Mexico. At least three Mexican citizens were killed in the incident, Mexican President Andres Manuel Lopez Obrador said on Twitter.

Speaking with CNN's Jake Tapper, Buttigieg, the openly gay mayor of South Bend, Indiana, said that America “can't go on like this.”

“We gotta change our thinking,” Buttigieg said. “We can absolutely honor Second Amendment rights for responsible gun owners without shooting down even the most basic, common-sense measures to save American lives, including our children, or we can fail yet again. The choice is right in front of us. The question is whether we're serious about this or not. We can't go on like this.”

In a tweet promoting his appearance, Buttigieg added: “Will the President of the United States leave his golf resort, go back to Washington, address the nation, condemn – in no uncertain terms – white nationalism, and call for the Senate to convene tomorrow to enact at least the most basic gun safety reforms that most Americans want?”

On Monday, Trump lashed out the media, suggesting that unbiased news coverage contributed to the tragedy in El Paso and another shooting in Dayton, Ohio over the weekend.

“The Media has a big responsibility to life and safety in our Country,” he tweeted. “Fake News has contributed greatly to the anger and rage that has built up over many years. News coverage has got to start being fair, balanced and unbiased, or these terrible problems will only get worse!”

In another tweet, Trump called on lawmakers to approve “strong background checks” on gun purchasers and “marrying this legislation with desperately needed immigration reform.”

Other Democratic presidential candidates, including New Jersey Senator Cory Booker and former Representative Beto O'Rourke, have said that Trump's anti-immigrant rhetoric played a part in the shootings.