So who is Allen Weisselberg, the long-time chief financial officer of the Trump Organization?

Weisselberg has been working with the Trump family since the 1980s, at which time he was hired to work with Trump’s father, Fred, in his real estate firm. He later moved to the Trump Organization, where he reported directly to Trump, according to the Wall Street Journal. He has served as the firm’s CFO for years, taking on more responsibility—along with Donald Trump Jr. and Eric Trump—after the president’s election in 2016.

Over the years, Weisselberg’s role in the family’s organization has evolved considerably. The WSJ reports that he has assumed a variety of duties, from “arranging for checks that Mr. Trump would sign,” to handling “dealings with banks and other important matters.” Weisselberg also reportedly oversaw many of Trump’s personal matters, including household expenses and personal purchases. He even prepared Trump’s tax returns for some time.

Weisselberg has long been seen as loyal to the family and organization, with Trump writing in his 2004 book Think Like A Billionaire, that Weisselberg “has been with me for thirty years and knows how to get things done.” A WSJ source has called Weisselberg “the most senior person in the organization that’s not a Trump,” demonstrating his close ties to the family.

In addition to his role at the Trump Organization, Weisselberg also served as treasurer of the Donald J. Trump Foundation, which is the subject of a lawsuit by the New York Attorney General’s office. He was also on the board of the Miss Universe Organization during the period in which the pageant was owned by Trump, and was once a vice president of Trump’s Atlantic City casino company.

Weisselberg is now considered a witness in the ongoing investigation of Cohen for possible bank fraud and campaign finance violations. It is unclear whether he has already appeared before the grand jury or not, nor what questions will be or have been asked of him.