John Barnett was found dead in his car in the parking lot of the Charleston, South Carolina, hotel where he was staying while giving testimony in a whistleblower case against aircraft manufacturer Boeing. Authorities are still investigating the cause of death, but Barnett’s mother, Vicky Stokes, said she already holds the company responsible for it. “If this hadn’t gone on so long, I’d still have my son, and my sons would have their brother and we wouldn’t be sitting here,” she told CBS News when asked if she blamed Boeing. “So in that respect, I do,” she said. Barnett, who was 62 when he died…