Boeing Whistleblower Dies by Suicide Amid Involvement in Lawsuit with Company

A whistleblower who was at war with Boeing died last week -- and investigators say it appears he took his own life, this while he was embroiled in a lawsuit against the company.

John Barnett was discovered dead on Saturday out in Charleston, SC -- where cops say his body was found in his truck in a hotel parking lot ... with him suffering an apparent self-inflicted gunshot wound. No word on if foul play is suspected -- but police are investigating.

Barnett's attorney, Brian Knowles, called the passing of his client "tragic" ... and went on to express explicit doubt about the circumstances of his death, making sure to call the self-inflicted gunshot wound cops are citing as "alleged."

What's more startling is Barnett was literally in the midst of a whistleblower lawsuit against Boeing -- his former employer of 32 years -- as he was alleging retaliation for sounding the alarm on what he characterized as cutting corners on assembly lines for their planes.

This is a drum Barnett had been beating for a long time -- and he even came on "TMZ Live" recently to address issues that Boeing's 737 Max aircraft had been experiencing lately.

Of course, the one incident that comes to mind is a door blowing off a 737 flight mid-air in January ... which left the passengers clinging to dear life as the plane tried to land safely.

Barnett -- a former quality manager at Boeing -- spoke with us and said he wasn't surprised by the mishap ... alleging he'd seen Boeing turn a blind eye to safety concerns for years. He also told us that Boeing's 737 Max aircraft being given the green light to fly again so soon after the Alaska Airlines incident was alarming ... suggesting it might've been unsafe.

Fast-forward to last week ... when Barnett was in the middle of depositions in his case against Boeing. The company released a statement and said it was saddened by his death.

He was 62.