An employment tribunal has heard details of infighting at the Wrexham-based British Association for Shooting and Conservation (BASC).
Former acting assistant chief constable of north Wales, Steve Curtis, allegedly swore at and threatened a colleague.
He is claiming unfair dismissal.
The tribunal in Chester was told Mr Curtis, of St Asaph, Denbighshire, resigned from his job as human resources director at the Rossett charity - which has 145,000 members - just as he was about to be dismissed in May 2016.
It heard claims he clashed with north of England regional director Alasdair Mitchell at a staff meeting in October 2014 and said: "I swear I will kill you."
The tribunal was also told Mr Mitchell resigned in December 2015.
Richard Ali, who was chief executive, and Gary Ashton, another former senior police officer and director at the BASC, were both subsequently suspended and remain so.
Mr Curtis said he was assessed as "outstanding" during his time at the association, adding that he could not remember threatening to kill Mr Mitchell.
"I was mortified when I later discovered what I had apparently said," he said.
But Mr Mitchell claimed he had been "a source of a number of difficulties from an operational and HR perspective".
Two separate inquiries were held, one of them by independent solicitors Hill Dickinson, which both exonerated Mr Curtis.
Mr Curtis said a refusal by the charity's council to accept the findings of the independent investigations convinced him he had no choice but to resign.
"I am still the victim of a continuing campaign to damage my reputation," he added.
The hearing is expected to last several days.
A former high-ranking police officer has claimed there was a conspiracy to oust him from his job at a shooting and countryside charity.