Marcel von Allmen was a member of the "Ordens der arischen Ritter" - Order of Aryan Knights, in English. The group had earlier attempted to murder a Yugoslav man, and spent a great deal of time plotting to murder a Swiss man. The leader had recently received a suspended sentence for shooting at a police officer.
Marcel was, apparently, starting to catch on that his group was bad news and trying to leave. They attempted to lure him to a meeting on January 26th, but he didn't want to come (perhaps he had prior plans that did not involve being murdered that night?). On the night of January 27th-28th, though, he gave in to the group leader's request for a meeting.
His fellow Nazis beat him brutally, then packed him up in one of their cars for a trip to Lake Thun. There, they weighted him down and dropped him into the lake.
Shortly after his body was found, the rest of the Aryan Knights were arrested. Last we heard, the leader's attempt to appeal his life sentence was rejected. Apparently "the prosecution's witnesses don't like Nazis" is not grounds for a reduced sentence. Who would have thought?