He doesn't appear to be a 'counter protester' but a neo-video journalist (I don't know what to call journalists any more since I see so many grammatical errors in AP stories...).

It looks like to me that he felt physically threatened, lost his cool and pulled his gun. Details aren't so clear from the video but you could see several men acting physically intimidating to the one who captured it all. Clearly, there was some provocation at the very start but I couldn't tell what it was. Anyone know?

If you were afraid of being attacked by multiple people, wouldn't you pull out a weapon? Ultimately, I think that is why the charges are going to be dropped.