stolen rifle?
When Captain Arseniev came in to identify Dersu Uzala's body, he asked the policeman where Dersu's rifle was. The policeman said that it wasn't found and suggested that Dersu was murdered and the rifle was stolen.
Since we're not given any details as to the circumstances of Dersu's death, an equally likely explanation is that the policeman found (and stole) the rifle upon discovering Dersu's body.
The film is based on a true story, so I wonder if there was any evidence that Dersu was actually murdered.