The upheaval at the National Rifle Association claimed its latest casualty Thursday with the announced resignation of David Lehman, general counsel of the NRA Institute for Legislative Action in Washington, D.C., the group’s powerful lobbying arm.

Lehman, who was with the nonprofit organization for 17 years, is the latest in a string of lawyers, executives and board members to leave the troubled NRA in the past four months. He could not be reached for comment Friday.