I don’t think this is proof. It could just be a person who looks similar. The title also asks the question. I do not think anyone should post this as proof. It is just a similar looking person in the same state.
50 seconds into this speaking to LEO:
You are right, there us no DNA or fingerprints in this video.
However the shooter lived in NV near where Trump rally was taking place, has the same face structure as in video, same beard, same color of facial hair, same ear structure etc.
So there is definitely motive to murder mostly white, mostly republicans gathered in large number (22,000) for this anti-Trumper in video at 0.53+
http://www.ktvn.com/story/36203418/president-trump-supporters-and-protesters-gather-in-reno