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Previous reporting by The Times and others has chronicled the internal tumult around Mr. North’s departure. But the new documents show a deeper level of coordination than was previously known in the effort against Mr. LaPierre, with extensive discussions between Mr. North’s allies and the N.R.A.’s own outside counsels. Mr. Cooper and other lawyers exchanged emails urging leaks and countermeasures that would undermine Mr. LaPierre’s strategy. At one point in April Mr. Cooper wrote another lawyer in frustration, saying, “No one on our side will leak.”

The documents also show how Mr. LaPierre scrambled to shore up his standing, reaching out to board members for support. And handwritten notes taken by an aide to Mr. LaPierre, scrawled on a yellow legal pad, detailed what the N.R.A. says were threats made by Mr. North to force Mr. LaPierre to resign. There would be revelations about “sexual offenses” by one of Mr. LaPierre’s colleagues, about spending on “Wayne/clothing” and luxury travel. Mr. North sought the “immediate resignation of Wayne,” the notes said, adding, “Window is short.”

Mr. Cooper, in a statement on Thursday, said, “Throughout the over three decades in which I have represented the N.R.A., I have adhered to the highest standards of professionalism.” He added that he owed an “ethical duty of loyalty to the N.R.A. itself” and not to “any individual officers or directors.”

Michael Volkov, an outside counsel who resigned Thursday, declined to comment, as did Brendan Sullivan, a lawyer for Mr. North.

In legal filings, Mr. North’s lawyers have said that suggestions he took part in a coup attempt against Mr. LaPierre are “fictitious,” and that he had legitimate concerns about “potential financial misconduct” and was thwarted by Mr. LaPierre’s “total dictatorial control.”

Mr. LaPierre said in a statement that he was disturbed “that the N.R.A.’s supposed ‘friends’” engaged in what he called a “scheme to harm our Association,” and said Mr. North “abused the trust” of the gun group.

A spokeswoman for Mr. Cox referred to an earlier statement, when he said allegations that he was complicit in a coup attempt against Mr. LaPierre were “offensive and patently false.”