Boeing whistleblower John Barnett made a grim prediction that he could potentially end up dead after raising safety concerns about the jetliner giant, allegedly telling a family friend: “If anything happens, it’s not suicide.”

Barnett, 62, was found dead in his pickup truck in a Charleston, South Carolina, hotel parking lot on March 9 — the same day he was due to conclude his closed-door testimony in a lawsuit slapped against his former employer.

Authorities — who are still probing his death — initially said Barnett died from a “self-inflicted” gunshot wound to the head, but his lawyers, family, and friends have since raised doubts over whether the ex-Boeing quality control engineer actually took his own life.