Wallander (2008)

S01E03 One Step Behind

While enjoying a whimsical picnic in the woods, three young friends are tragically gunned down. Their bodies are discovered, along with the lifeless form of another acquaintance who had confided in Wallander about a colleague's secret life as a gay transvestite. This individual, now revealed to be dangerously unstable, continues his rampage by claiming the lives of three more innocent victims.