Senators on Wednesday triggered a U.S. government investigation into what happened to a prominent missing Saudi journalist, who is suspected to have been murdered last week in Turkey.

The lawmakers said they expect the investigation to look into the actions of the “highest-ranking officials in the government of Saudi Arabia,” a move that signals lawmakers on both sides of aisle are willing to confront the staunch ally.

The Republican and Democratic leaders of the Senate Foreign Relations Committee and the Appropriations subcommittee with responsibility for the State Department sent a letter to President Donald Trump that triggered a provision of 2016 Magnitsky human rights law.

That provision requires the president to reach a determination within four months on whether an extrajudicial killing has occurred against any individual who promotes human rights, including through freedom of expression, such as the missing Saudi journalist, Jamal Khashoggi. If an assassination is found to have occurred, the law requires the president to decide whether to impose sanctions on any individuals complicit in the death.

In their letter, Sens. Bob Corker, R-Tenn., Robert Menendez, D-N.J., Lindsey Graham, R-S.C., and Patrick J. Leahy, D-Vt., write that the disappearance of Khashoggi, who has not been seen since last week when he sought a legal document from the Saudi consulate in Istanbul, “suggests that he could be a victim of a gross violation of internationally recognized human rights.”

“Therefore, we request that you make a determination on the imposition of sanctions pursuant to the Global Magnitsky Human Rights Accountability Act with respect to any foreign person responsible for such a violation related to Mr. Khashoggi,” the senators wrote.

The letter is co-signed by nine Republicans and nine Democrats, including nearly everyone on the Foreign Relations Committee, with the exception of Sen. Rand Paul, R-Ky. Paul on Wednesday in a tweet called for ending arms sales to Saudi Arabia.

Turkey has accused the highest levels of the Saudi government of being involved in Khashoggi’s disappearance.

“I’ve shared with them [the Saudis] that they are at a very, very low point as it relates to political support here in the Senate, the lowest ever,” said Corker, who chairs the Foreign Relations Committee. “This would drop it off the cliff.”

Arms sales at risk?

Further arms sales to Saudi Arabia are “definitely” at stake, and any consequences will be “significant and definite,” Corker told reporters.

Khashoggi fled Saudi Arabia last year after Saudi government officials warned him to stop criticizing the policies of Crown Prince Mohammed bin Salman.

Khashoggi then moved to Virginia but more recently was spending time in Turkey, where his fiancee lives. He went missing after visiting the Saudi consulate in Istanbul last week to obtain a document necessary for his marriage. The Turkish government has concluded he was murdered inside the consulate.

Riyadh has denied involvement in Khashoggi’s disappearance but thus far has not provided any evidence to show that the journalist left the consulate. Turkish authorities have provided a video image purporting to show Khashoggi entering the consulate.

Over the years, Saudi Arabia has spent many billions of dollars purchasing U.S. weapon systems. Legislative attempts to block those sales have become a flashpoint for a growing number of lawmakers concerned about Saudi Arabia’s human rights record and its three-year war in Yemen, which has led to thousands of civilian deaths.

Trump and the State Department have said they are concerned by Khashoggi’s disappearance but have used less harsh rhetoric than senators in criticizing Riyadh.

On Tuesday, national security adviser John Bolton and White House senior adviser Jared Kushner spoke on the phone with Mohammed bin Salman to press him for information about Khashoggi, according to a Wednesday White House statement. Secretary of State Mike Pompeo also spoke with the prince “to reiterate the United States’ request for information” about the missing journalist.

Republican fury

Democrats for many months have been ahead of their Republican colleagues in criticizing Saudi Arabia’s human rights record and its ongoing war in Yemen.

But on Wednesday, a significant number of Republicans joined them in their criticism, signaling that they are prepared to take a tougher stand than Trump against Riyadh.

Graham said he planned to discuss the situation with the Saudi ambassador Wednesday evening.

“I don’t want to jump to conclusions, but it is very unnerving,” said Graham, one of the Senate’s biggest foreign policy hawks. “If something like that did happen, it would show complete contempt by the Kingdom of Saudi Arabia against international norms, it would show contempt for our relationship. It would be a game-changer for me.”

Senate Foreign Relations member Marco Rubio, R-Fla., said he is withholding final judgment until more facts become available, but “every day that goes by, it’s more concerning.”

“For someone to be murdered in a diplomatic facility overseas, I don’t know if that has any precedent,” Rubio said. “It would be an outrage. And it would impact the bilateral relationship, there’s no doubt about it, certainly here on Capitol Hill.”

Sen. Todd Young, R-Ind., who has led bipartisan efforts to prod Riyadh to do more to alleviate the humanitarian crisis in Yemen caused by its bombing campaign, said Saudi Arabia’s track record gave him good reason to be suspicious.

“I don’t give the Saudi leadership the benefit of the doubt on much of anything these days so I’m most concerned about their human rights record, about their manner of conducting the military operations in Yemen and about this latest news related to the Saudi journalist,” Young said.

Despite Trump and Kushner’s warm embrace of Salman as a critical regional ally against Iran, Corker suggested the Saudis have overestimated their importance to the United States, and that has caused them to take some actions that have alienated senators. He specifically noted that Menendez, the ranking member on the Foreign Relations Committee, had recently walked out of a meeting the two of them were scheduled to have with Saudi officials after they were late.

“I’ve noticed over the course of time that their posture here, certainly they felt very sure of themselves,” Corker said. “They view their status here as something that it isn’t.”

Sen. Christopher S. Murphy, D-Conn., has led multiple unsuccessful efforts to block the sale of precision-guided munitions to Saudi Arabia and to end U.S. military support of the country’s war in Yemen. But he said he now feels the tide is finally turning in the Senate

“Many of us have argued that we shouldn’t be giving the Saudis the benefit of the doubt, that they are in fact intentionally killing civilians,” Murphy said. “For those that were skeptical of whether the Saudis are intentionally killing civilians in Yemen, this might change their minds.”

But not all senators on Wednesday were quick to criticize Riyadh.

“Our relationship with the Saudis is very important, and we have to be very careful about it,” said Sen. Orrin G. Hatch, R-Utah, who is retiring. “We have to see who is responsible.”

Flashback: Earnest: Saudi Arabia Human Rights a ‘Significant Concern’

Ellyn Ferguson and John T. Bennett contributed to this report.