Senators called Sunday for swift and united action against Saudi Arabia if the United States determines that Saudi agents killed Washington Post columnist Jamal Khashoggi, with one Republican saying Treasury Secretary Steven Mnuchin should refuse to attend an economic summit in Riyadh this month until the facts are clear.

“I don’t think we should continue with business as usual until we know what happened here,” Sen. Marco Rubio (R-Fla.) said on CNN’s “State of the Union.”

“I don’t think he should go,” Rubio said when asked about Mnuchin’s plan to attend the conference.

Khashoggi, whose writings criticized the Saudi government, has not been seen since Oct. 2, when he walked into the Saudi Consulate in Istanbul to obtain a document for his upcoming wedding. Turkish authorities say a team of Saudis killed him, but the Saudi government has denied involvement.

President Trump, in excerpts of an interview with CBS News’s “60 Minutes” released Saturday, promised “severe punishment” for Saudi Arabia if the country is found responsible, but he said canceling arms sales to the kingdom, one proposed response, would be “very foolish” and would ultimately harm U.S. industries.

Rubio suggested that Trump should not rule out the possibility, saying, “Every option needs to be there in a response.” The senator, a member of the foreign relations and intelligence committees, he vowed that if Saudi Arabia is found guilty of Khashoggi’s death and the Trump administration does not respond, Congress would step in.

“It can’t be symbolic,” Rubio said of the administration’s response. “It can’t be just words.”

Sens. Bernie Sanders (I-Vt.) and Jeff Flake (R-Ariz.) also called for a robust response if the Saudi government is found responsible, including limiting or suspending arms sales and reconsidering U.S. involvement in the civil war in Yemen.

“Severe action needs to be taken,” Flake said on ABC News’s “This Week.” He said the Saudis’ explanation for Khashoggi’s disappearance “just isn’t plausible.”

Former CIA director John Brennan agreed.

“If Khashoggi had disappeared in Turkey when he was at a hotel or a private residence, I think there is plausible deniability on the part of the Saudi government. But he disappeared when there is video evidence of him being at the consulate,” Brennan said on NBC News’s “Meet the Press.”

“Their denials ring hollow, very much ring hollow,” he said.

White House economic adviser Larry Kudlow told “Fox News Sunday” that Trump is “very, very serious” about retaliating against the Saudis if they are found responsible.

On “Meet the Press,” he said Mnuchin would “make up his mind” this week about whether to attend the conference “as new information surfaces.”

Felicia Sonmez contributed to this report.