Former U.S. President Donald Trump speaks during a rally in Cullman, AL.

Marvin Gentry | Reuters

Matthew Calamari Jr., the Trump Organization’s director of security and son of its chief operating officer, is expected to testify Thursday before a grand jury in Manhattan investigating former President Donald Trump’s company, a person with direct knowledge of the matter said on Wednesday across from CNBC.

A subpoena was served on Calamari Jr. earlier this week to testify, the person said.

The person declined to be named to discuss the grand jury’s secret process.

The ongoing investigation comes two months after the Trump Organization and its CFO Allen Weisselberg were charged with allegedly 15 years of tax avoidance. Wei├čelberg and the Trump Organization have pleaded not guilty.

Calamari Jr.’s testimony could provide him with vital immunity protection in the extensive and longstanding criminal investigation conducted by Manhattan’s District Attorney Cyrus Vance Jr.

New York attorney general Letitia James is also investigating Trump’s company “in a criminal capacity”.

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A spokesman for Vance’s office declined to comment. The Trump Organization did not immediately respond to a request for comment on the testimony.

The Wall Street Journal, which first reported on Wednesday that Calamari Jr. is expected to testify this week, also reported that Trump Organization senior finance officer Jeffrey McConney is expected to stand before the grand jury this week as well.

Prosecutors are investigating how Calamari Jr. reported his taxes on an apartment he received from Trump’s company, the Journal reported.

McConney prepared Matthew Calamari Sr.’s personal tax returns, according to the newspaper.

The elderly calamari was reportedly under investigation by prosecutors to determine whether he violated tax laws while taking advantage of the company.