NRA board member Richard Childress, a former NASCAR driver and the owner of a self-titled car racing enterprise, submitted his resignation to the board, John Frazer—the organization’s secretary—and NRA President Carolyn Meadows on Monday, according to a copy of the letter obtained by Newsweek.

This marks the fifth resignation from the NRA’s board of directors since August 1, when three board members quit after they allege they were sidelined for raising questions about apparently lavish spending and mismanagement by top executives.

Childress, along with former NRA President Lt. Col. Oliver North, had previously authored a memorandum to the chairman of the NRA’s audit committee and Frazer (in his dual capacity as general counsel) expressing how they were “deeply concerned” about the billable hours being racked up by the organization’s outside counsel, William A. Brewer III.