As the investigation of the alleged coordination between Donald Trump’s presidential campaign and Russia during the 2016 election continues to unfold at a glacial pace, another development has surfaced.  Robert Mueller’s team has introduced a new name into the fold: California real estate investor Tom Barrack.

Barrack, who had a big presence at last week’s Milken Institute Global Conference in Beverly Hills, is one of Trump’s closest confidants and has been interviewed by investigators working for Mueller, according to the Associated Press. The specifics about Barrack’s interview remain private, but three anonymous sources spoke to the AP said the questioning focused on Paul Manafort and Rick Gates, two officials from Trump’s campaign who have been indicted by Mueller. In February, Gates pled guilty to federal conspiracy and false-statement charges in February and is now cooperating with investigators in the matter.

The AP says that, according to sources, Barrack was interviewed “months ago” and he was asked about Gates’ involvement in the inaugural committee, which Barrack directed.

As a top fundraiser in Trump’s 2016 campaign, Barrack played a big role in his election. Their relationship goes back to Trump’s real estate days. They met in 1988 when Barrack negotiated the sale of The Plaza Hotel in New York to Trump. Since then, they remained close friends and maintained a professional relationship. Barrack also spoke at the Republican convention in 2016 when Trump officially received his nomination.