U.S. Senator Elizabeth Warren is demanding Donald Trump ally Tom Barrack explain how he won business with Saudi Arabia’s sovereign wealth fund after working closely with the president and his administration.

In a letter to Barrack, the lawmaker highlighted deals the financier’s Colony Capital Inc. arranged after he met with Saudi officials including Crown Prince Mohammed Bin Salman while serving as head of Trump’s inaugural committee and as an adviser to the presidential transition team. The transactions were the subject of a recent Bloomberg article.

“Your efforts to leverage your close friendship with the president and to boost your personal financial interests are deeply troubling and raise serious questions about the bounds of ethical behavior for presidential transition teams and advisers,” Warren wrote in the letter dated Aug. 14.