Former Trump campaign chief Paul Manafort has trouble in his own house. According to court documents, one of Manafort’s former employees led an FBI agent to a storage locker filled with paperwork on Manafort’s businesses and finances. The person’s name is redacted from the filings. But he’s now at the center of a fight over evidence that could play a significant role in the government’s case against Manafort.

“People do strange things when confronted with authoritative FBI agents,” said Sol Wisenberg, a criminal defense attorney with Nelson Mullins.

This makes the second Manafort associate known to have aided the government in the sprawling investigation into foreign influence in U.S. politics. Rick Gates, Manafort’s long-time right hand, began cooperating with Special Counsel Robert Mueller’s office in February.

Manafort’s attorneys revealed the information about the second former employee in an April 6, 2018, court filing. In the filing, Manafort’s attorneys asked the federal judge overseeing the prosecution to block documents found in a storage unit in Alexandria, Virginia, from being used as evidence against him. They argue the employee did not have the authority to let the FBI agent look into the storage unit, and that, therefore, the FBI violated Manafort’s Fourth Amendment rights.

Manafort’s filing includes a heavily redacted affidavit signed by an FBI special agent on May 27, 2017. In that affidavit, the FBI agent explains how he learned about a storage unit full of documents from Manafort.

The agent describes meeting with “a former employee of Davis Manafort Partners, and a current employee of Steam Mountain, LLC, which is a business currently operated by Paul Manafort.” The employee, whose name is redacted throughout the affidavit, told the FBI agent that he “performs a variety of functions for Manafort and his companies as directed by Manafort,” and was salaried.

That employee moved boxes of files from one storage unit to a second, larger storage unit in Alexandria. On May 26, 2017—just nine days after Rod Rosenstein named Bob Mueller special counsel—the person whose name was redacted led the FBI agent to the storage facility. The facility’s manager gave the FBI agent a copy of the lease for the storage unit.

“The lease identifies [REDACTED] as the occupant of Unit 3013, and also identifies Paul Manafort as a person with authorized access to Unit 3013,” the application says. “Rick Gates is listed as an alternate point of contact for the lease.”

“ One box was marked as containing expenses, paid bills, invoices, and legal complaints. Another box was had info on the ‘Ukraine Campaign.’ ”

The person whose name was redacted also gave the FBI agent “a key to the lock on Unit 3013 and described the contents of Unit 3013,” according to the affidavit. That person also gave the FBI agent “written consent” to search the storage unit, and opened it for the FBI agent.

The FBI agent then looked into the storage unit and saw about 21 boxes of documents, as well as a filing cabinet. One box was marked as containing expenses, paid bills, invoices, and legal complaints. Another box said it contained “Ukraine Binders,” as well information about ballot security, Georgia, research, and “Ukraine Campaign.”

Manafort and Gates have been involved in Ukrainian politics for years, and helped prop up Kiev’s Putin-friendly strongman, Viktor Yanukovych.

The FBI agent seemed to figure out immediately that the storage unit’s contents were interesting, because the law enforcement officials started surveilling the storage unit facility to see if anyone went in to take out any files. The day after seeing the storage unit, the FBI agent filed the affidavit—which was more than 20 pages long—with a magistrate judge.

Though the name of the Manafort employee who showed the storage unit to the FBI was redacted in the affidavit, another exhibit Manafort’s lawyers filed appears to have that person’s name unredacted. The affidavit said the person who showed the FBI the storage unit was listed on the lease as the “occupant” of the storage unit. Manafort’s lawyers also filed the lease with the court as part of their motion to suppress the storage unit evidence. And the lease name a man named Alexander Trusko as the storage unit’s “Occupant.” The lease also names Rick Gates and Paul Manafort as having access to the storage unit. (Trusko could not be immediately reached for comment.)

Manafort’s lawyers are arguing that the former employee didn’t have the authority to let the FBI agent look inside the storage unit. The lawyers describe the one-time employee as “low-level” and responsible for “administrative functions.” They argue that the FBI agent violated Manafort’s Fourth Amendment rights by looking into the storage unit, and that the former employee didn’t have the lawful authority to let the FBI agent look into the storage unit.

“[T]he former employee had no such authority, and the FBI Agent knew it,” Manafort’s lawyers wrote.