In 1988, Gossett changed his name to "Wolfgang" and became a Roman Catholic priest, which Cook and others interpreted as an effort to disguise his identity. Other circumstantial evidence includes testimony that Cook claims to have obtained from William Mitchell, a passenger on the hijacked aircraft, regarding a mysterious "physical detail" (which he will not divulge) common to the hijacker and Gossett. Cook also claims to have found "possible links" to Gossett in each of four letters signed by "D.B. Cooper" and mailed to three newspapers within days after the hijacking, although there is no evidence that the actual hijacker created or mailed any of the letters.