A law enforcement investigation has concluded that the death of the first of two Boeing whistleblowers earlier this year was due to suicide, according to police documents released Friday. John Barnett, 62, was discovered dead with a gunshot wound to the head in his car in the parking lot of his hotel in early March. He had been giving a deposition in Charleston, South Carolina, at the time in his whistleblower lawsuit against Boeing. Charleston police determined the death was a suicide because the gun was determined to have been fired by Barnett in his locked vehicle, and he was found with a m…