How is flashing your camera at the conductor supposed to warn him of an impending accident?
First, there is no way for the conductor to make the connection between a flashing camera and a human obstruction on the track.
Second, and more importantly, the flash of the camera probably distracted the driver's attention. He might not have seen the man in front of him because he was too busy looking at some yahoo taking pictures.
So, in theory, it might be said that the photographer's actions contributed to the man's death.