The longest-serving member of the Louisiana State Police Commission stepped down Thursday, leaving the commission with its second vacancy in as many months at a time of increasing strife among the board. 

The seven-member board hears complaints from rank-and-file troopers and has final authority over civil service matters. 

Donald Breaux, 79, of Lafayette, attributed his resignation to "personal reasons" in a letter to the commission's chairman. But he acknowledged in a telephone interview Friday that he has grown weary of the infighting on the commission, whose most recent meetings have been marked by heated debate and procedural confusion.    

"I've had a good run," Breaux said. "They will build a commission that's very functional before it's over with."

Breaux, a former state trooper and sheriff of Lafayette Parish, was appointed to the commission in 2014. He also was a past president of the Louisiana State Troopers Association, a nonprofit organization that received a series of grand jury subpoenas Wednesday from federal authorities. 

But Breaux said he was not among the current or former LSTA officials to receive subpoenas, which stemmed from a months-old federal inquiry into unlawful campaign contributions.

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He said he decided last week he would step down due to a health issue.

Breaux's resignation furthered the revolving door of leadership on the board that enforces State Police rules. It came weeks after another board member, W. Lloyd Grafton, publicly questioned the integrity of the commission as he announced his own resignation.

Grafton expressed concerns that State Police leadership and the troopers association exert too much influence over the commission.

In January, the commission's longtime executive director, Cathy Derbonne, resigned moments before board members were scheduled to discuss her "professional competence." She said she was convinced the board had been poised to fire her for helping facilitate an investigation into unlawful campaign contributions by three members of the commission.

Those members also resigned after it emerged that they improperly gave thousands of dollars to political candidates in violation of state law.

The troopers association also made unlawful contributions and was fined $5,000 in January by the State Ethics Board. 

Follow Jim Mustian on Twitter, @JimMustian.