Of all of the hikers, Zolotaryov is the most mysterious. His only son, Sasha, was missing and it was said he was in Germany, which would be a reason for Zolotaryov to want to get out of Russia, perhaps with the CIA and rejoin his son. there were strange dynamics in his relationship with his wife and daughters. That being said, he did have a pen and paper notebook found on his person and there was only one person who ever saw it, I cannot name that investigator, but he allegedly grabbed the paper, screamed "he wrote nothing," or something similar and threw it away or stuck it in his pocket. What else would go along with this theory is the diaries saying the guys were arguing and fighting. What were they fighting about? Did some of them figure out what Zolotaryov had and were concerned?
As far as the pictures of lights, it is possible it could be a helicopter. I thought it might have been a photo Zolotaryov took from the ravine as the KGB or killers were walking away after bludgeoning everyone in the ravine.
At this time, without more information, all thoughts and speculation are just that. To solve this mystery, more information needs to be found through the Russian government sources. I would pray that would happen....