Why would a #whistleblower kill himself while testifying in a lawsuit against his former employer?

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.

https://www.bbc.com/news/business-68534703