John Barnett had worked for Boeing for 32 years, until his retirement in 2017.
In the days before his death, he had been giving evidence in a whistleblower lawsuit against the company.
Boeing said it was saddened to hear of Mr Barnett’s passing. The Charleston County coroner confirmed his death to the BBC on Monday.
It said the 62-year-old had died from a “self-inflicted” wound on 9 March and police were investigating.
First whistleblower “suicide”?
The second I see someone’s name next to whistleblower, I know they’re on borrowed time, some manage to be left alone, but most don’t, that’s why we need to keep these people’s names and causes alive, we can’t let corporations get away with silencing a whistleblower, we must amplify it.