The emails, released by Donald Trump Jr., are the most concrete evidence yet that Trump campaign officials welcomed Russian help to win the election, a subject that has cast a cloud over Trump’s presidency and spurred investigations by the Justice Department and Congress.

The messages show that the younger Trump was open to the prospect of “very high level and sensitive information” from a Russian attorney that a go-between described as “part of Russia and its government’s support for Mr. Trump” ahead of a meeting on June 9, 2016.

“If it’s what you say I love it,” Trump Jr. responded. He released the messages on Twitter after the New York Times said it planned to write about them and sought comment from him.

In an interview with Fox News, Trump Jr. said that Trump’s campaign manager at the time, Paul Manafort, and son-in-law Jared Kushner, now a top White House adviser, also attended the meeting with Russian lawyer Natalia Veselnitskaya, who denies having Kremlin ties.

He said Veselnitskaya did not provide any damaging information about Clinton at the meeting and instead sought to discuss Russian sanctions.

“In retrospect, I probably would have done things a little differently,” he said. “For me, this was opposition research.”

Nevertheless, the correspondence between him and Rob Goldstone, a publicist who arranged the meeting, could provide fodder for U.S. investigators probing whether Trump’s campaign colluded with the Kremlin.

“The crown prosecutor of Russia … offered to provide the Trump campaign with some official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to your father,” Goldstone wrote Trump Jr. on June 3. Russia does not have a “crown prosecutor” – the equivalent title is prosecutor general.

U.S. intelligence agencies have concluded that Moscow sought to help Trump win the election, in part by releasing private emails from Democratic Party officials.

“The conversation will now turn to whether President Trump was personally involved or not. But the question of the campaign’s involvement appears settled now,” Cornell Law School professor Jens David Ohlin said in an interview.

“The answer is yes.”

Moscow has denied any interference, and Trump says his campaign did not collude with Russia.

Trump Jr. said he did not tell his father about the meeting. He said he may have since had contact with other Russians.

“I’ve probably met with other people from Russia, but certainly not in the context of actual formalized meetings or anything,” he said on Fox News.

Financial markets jolted

The news jarred financial markets as investors worried it presented a fresh distraction from the administration’s economic agenda.

Stocks and the dollar fell, while U.S. Treasury securities gained ground. Stocks later retraced most of their losses after Senate Majority Leader Mitch McConnell pledged to keep lawmakers in Washington longer than scheduled to push through a bill to overhaul healthcare.

Along with his younger brother Eric, Trump Jr. oversees the Trump Organization, his father’s real-estate and business empire, and does not have a formal role in the White House.

“My son is a high-quality person and I applaud his transparency,” Trump said in a statement. The White House referred questions to lawyers for Trump and his son.

The emails do not appear to provide evidence of illegal activity, but legal experts say Trump Jr. could run into trouble if investigators find he aided a criminal action, such as hacking into Democratic computer networks, or violated campaign-finance laws by accepting gifts from foreign entities.

He is likely to face scrutiny from both congressional committees investigating the matter.

The Senate Intelligence Committee plans to call on him to testify and to provide documents, according to a Senate source, while the House of Representatives Intelligence Committee wants to interview him and everybody else involved in the meeting, said the panel’s top Democrat, Representative Adam Schiff.

“The American people need to know that our president is acting on their behalf and not acting because he has a fear that the Russians could disclose things that would harm him or his family,” Schiff told reporters.

On Fox News, Trump Jr. said he was “more than happy to cooperate with everyone.”

Senate Judiciary Committee Chairman Charles Grassley, a Republican, asked the Trump administration how Veselnitskaya was able to enter the United States even though her authorization had expired.

CNN reported that Special Counsel Robert Mueller, who is heading a criminal investigation at the Justice Department, also planned to look into the meeting.

Vice President Mike Pence, who has said the campaign had no contacts with Russia, said through a spokesman he was not aware of the meeting, held before he became Trump’s running mate later that summer.

Senator Lindsey Graham, a South Carolina Republican who is at times harshly critical of Trump, told reporters: “This is very problematic. We cannot allow foreign governments to reach out to anybody’s campaign and say: ‘We’d like to help you.'”