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’ve thought about this way too much and if you seriously think you’re in danger, there’s a few things you can do. Obviously lots of security cameras with local and off-site backups. Then hidden cameras, whatever spy cameras you can find, with an SD card in each. Then you need to create a deadman switch. Something you must interact with at least daily or it automatically uploads all your videos and documents etc everywhere it can, and / or sends them to your lawyer or journalists if you think you can trust them. I err on the side of public release as well because as long as it’s in the public eye it will be subject to scrutiny. That’s also why I’d start establishing a social media presence. “HI I’m X, I blew the whistle on Y. There’s a hearing scheduled for Z and I would like to once again publicly state that I don’t have any current medical or mental health issues and I have no plans to ever take my own life. Anyway here’s how to make waffles” or whatever.