Anja Kofmel was only 10 when her cousin Chris, an adventurer who she hero-worshipped, was found shot in the head in a snow-fringed field in Croatia.
As she grew up, the Swiss animator became fascinated by how an idealistic young reporter somehow ended up in a Croatian paramilitary unit accused of the ethnic cleansing of Serb villagers as the former Yugoslavia fell apart.
Kofmel's new film about her cousin, "Chris the Swiss" -- which is showing this week at the world's top animation festival in Annecy, France -- has been hailed by the Hollywood Reporter as a "stirring suspenseful and moving elegy for doomed youth".
But it also raises uncomfortable questions about what exactly Christian Wurtenberg was up to and about the shadowy involvement of the Catholic group Opus Dei in the war.
Kofmel's investigation into the strange and murky world in which her cousin died not only reopened old wounds for her family but also led her to the jailed terrorist "Carlos the Jackal" -- Ilich Ramirez Sanchez -- and ultimately on the trail of a hitman who tried to overthrow Bolivian President Evo Morales in 2009.
Throbbing in the background was the knowledge that British photographer Paul Jenks -- who had also tried to find answers about her cousin's murder -- ended up with a bullet in his head.
Kofmel begins the steadily darkening story from a child's point of view, using animation as well as interviews with war reporters and former mercenaries and volunteers who fought with Wurtenberg in the Croatian First Platoon of International Volunteers (PIV) near Osijek in the winter of 1991.
- 'He was my hero' -
"I looked up to him, Chris was my hero," Kofmel told AFP. "He was my big cousin who was an adventurous exciting guy for a little girl like me.
"Later I realised he was not just black and white."
Using his diaries and notes, the film reconstructs her cousin's path from being a greenhorn journalist filing reports on the war for Swiss public radio to his fateful meeting with Eduardo Rozza Flores, aka "Chico", a former KGB trainee who set up the PIV with a motley crew of far-right activists drawn to defend "Catholic Croatia" from Slobodan Milosevic's Serbia.
Chico, a mysterious Hungarian-Bolivian whose father was a friend of Che Guevara, is the film's dark heart.
Like Wurtenberg, he apparently came to Croatia to try his hand as a reporter before quickly realising he preferred making war to covering it.
Kofmel suspects her cousin was killed by Chico when he discovered that he had joined his unit to expose the atrocities it was committing.
"Chris was trying to write a book. I can see it from his notes. We don't have his manuscript. I don't know if he was close to finding something, or if there was a huge story.
"I know certain things. Chico was a member of Opus Dei. I think this is why Christian died, I think he wanted to prove that they were being financed by Opus Dei," she said.
- Coup plot -
Kofmel, however, has no proof to back her theory. "I didn't find anyone who admitted that they paid for the weapons for those massacres. I have some hints, and Opus Dei priests came to see them, but not more.
"In war it doesn't take much to get killed. Maybe there was someone who didn't like him," Kofmel added.
However, Carlos the Jackal -- a friend of Chico's -- told her from his prison cell in France that her cousin was killed because he was Swiss spy.
The only person who really knows, Chico, brought his secrets to the grave. He was killed by Bolivian special forces in a hotel room in Santa Cruz in 2009 where they said he was plotting with far-right Croatian exiles to kill President Morales.
Despite spending years chasing down clues, Kofmel said much about her cousin -- and his death -- remains hazy.
"On the one hand he was a very smart guy and on the other I wonder if he was really aware of what he was getting into. I don't get him still," she said.
"I think what drove him was the question of how humans can be so violent and cruel. How can neighbours one day start killing each other? It is not just the Croats and the Serbs, it's all of us. Civilisation is so thin. We don't like to think about it, but we have this potential for brutality."
Anja Kofmel's 'Chris the Swiss' is just one of huge array of animated films and filmmakers at the Annecy Festival
Kofmel interviewed Venezuelan terrorist "Carlos the Jackal for her book (1970s picture)