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.
I didn’t say they did although I would personally place it at like a 60% likelihood. Obviously there’s no evidence, this literally just happened.
Just wanted to be clear that I live in reality and no one has the security camera footage yet.