It’s the company’s long-time chief financial officer and his son, Allen and Barry Weisselberg, versus the chief operating officer and his son, Matthew Calamari Sr. and Jr.

The target of this three-year criminal investigation has always seemed to be former President Donald Trump himself. To nail him, investigators might need to flip Allen Weisselberg, his right-hand finance man. But to get that guy, they’ll need to leverage his deputy, the accountant Jeffrey S. McConney. And it looks like they’ve found an avenue to pressure him: “Matty” Calamari Jr.

According to two people familiar with the matter, prosecutors are trying to use the Trump Organization’s young head of corporate security, Matty, to elicit damning information about the company’s controller, McConney. One of those sources said Matty’s only tie to McConney is that the accountant prepared his individual taxes years ago—and prosecutors are exploring whether those taxes accurately reported details about his residency and corporate apartment and vehicle.

Hence why “Matty Jr.” was subpoenaed to testify before the grand jury on Sept. 2. McConney was also brought in a second time later that same day, according to this person.