A former executive of William Koch’s Oxbow energy company alleges in a lawsuit that he was “interrogated” and “imprisioned” by Koch for two days at his aspen estate. Kirby Martensen, the former executive, filed the lawsuit last week against William Koch. While at “Bear Ranch,” Martensen alleges in the complaint that he was “escorted to a small room and interviewed by two agents of Koch. The interview turned into an interrogation that lasted several hours.”  Afterward, he was escorted to an SUV and “served with his termination papers and a lawsuit.”