A person claimed by Keith Waldemar Mangnoson to be the Somerton man. Mangnoson believed he and Thompsen had worked together in Remark in 1939. Not long after this, Mr Mangnoson and his son Clive disappeared. They were found some days later. Mr Mangnoson was still alive but his son had died.
Following Keith Mangnoson being admitted to an asylum, his wife Roma Mangnoson, reported being threatened by a masked man, who, while driving a battered cream car, almost ran her down outside her home in Cheapside Street, Largs North. Mrs Mangnoson stated that "the car stopped and a man with a khaki handkerchief over his face told her to 'keep away from the police or else.' Additionally a similar looking man had been recently seen lurking around the house. Mrs. Mangnoson believed that the situation was related to her husband's attempt to identify the Somerton Man. J. M. Gower, secretary of the Largs North Progress Association also received anonymous phone calls threatening that Mrs. Mangnoson would meet with an accident if he interfered while A. H. Curtis, the acting mayor of Port Adelaide received three anonymous phone calls threatening "an accident" if he "stuck his nose into the Mangnoson affair."
If all of these events are connected to Mr Mangnoson's attempts at identifying the Somerton Man, then it seems that someone really did not want him identified. Perhaps Mr Mangnoson knew something he shouldn't.
According to test carried out by Prof. Abbott and his students on hairs extracted from the Somerton Man's cast, at some point prior to the Somerton Man's death he had been exposed to Arsenic and Lead. Although this was probably not the cause of his death, it may add some weight to the idea that the Somerton Man had been a farm labourer as Lead Arsenate was a commonly used pesticide, particularly on apple trees to combat Codling Moths.