When asked by MSNBC if Trump is a white supremacist, O'Rourke responded without hesitating, "He is."

"He’s also made that very clear,” added the candidate. “He’s dehumanized or sought to dehumanize those who do not look like or pray like the majority here in this country."

Although O'Rourke has called Trump racist and a white nationalist in the past, he has stressed the point even more since the mass shooting in El Paso.

O'Rourke said that Trump's racist rhetoric inspired other acts of violence, adding that the El Paso attack was "not an isolated incident." He used the Tree of Life Synagogue shooting in Pittsburgh, Pennsylvania, and the arson attack on a mosque in Victoria, Texas, to prove his point.

The El Paso shooter's online manifesto describes how a large Hispanic population in Texas will make it a “Democratic stronghold” and that immigration and first-generation Americans are guilty of “blending cultures” in the US, CNN reported.

O'Rourke also pointed out how Trump laughed when someone yelled "Shoot them!" in reference to immigrants at a rally in May. "He says, ‘That’s OK with me," said O'Rourke.

"He’s not the source of racism in this country'– this country has been racist as long as it’s been a country. But he’s certainly fanning the flames. He’s certainly making violence like this more possible and more real."

Trump mocked O'Rourke's nickname as a "phony name to indicate Hispanic heritage” and urged him to “be quiet” after the challenger attacked the president for inciting violence at a vigil after the attack.

"22 people in my hometown are dead after an act of terror inspired by your racism,” tweeted O'Rourke in response. “El Paso will not be quiet – and neither will I.”

Hagay Hacohen contributed to this report.

Democratic presidential hopeful Beto O'Rourke called US President Donald Trump a white supremacist without hesitation in a live interview in El Paso, Texas, where a mass shooting killed 22 people, according to HuffPost.