Johan Martens was active in the debate about where Norway's main airport should be located (see some background about this case here). He informed the parliamentary commission led by Eivind Smith about threats against him (referred to in Knut Lindhs book "Hvem drepte Jan Wiborg?" (Who killed Jan Wiborg?) 2014 page 77.
In the commission's papers it is mentioned that Martens told that he and his wife received threatening phone calls four times. This happened 3-4 weeks before October 8 1992. The person calling Martens said that they were not pleased with Martens's engagement in the airport debate. Martens was also told that if he did not end his engagement, something could happen to him, and his children would be vulnerable.