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 Barnettâs passing. The Charleston County coroner confirmed his death to the BBC on Monday.
It said the 62-year-old had died from a âself-inflictedâ wound on 9 March and police were investigating.
Or, short of that⌠If youâre whistleblowing on Boeing, you should go to Airbus and Lockheed and tell them, âitâs in your best interest that I stay breathingâ.