Purely the fight sequence of events? I think so yes.
2 guys get into a fight. A firearm they are grappling over discharges. It hits an innocent bystander. The bystanders partner attacks the shooter. During the struggle they're killed. It's a logical sequence of events.
After Carol was killed RH and GL both had reason to think they had to kill to survive, Hill could reasonably think he will be next, Lynn could fear that he would be killed in retaliation.
What I'm not convinced Lynn is being truthful about is what lead to the fighting turning physical.
If I wanted to put forth the theory I believe most likely, I would say Lynn was very drunk, very annoyed with Russell and went to RH campsite with his shotgun in a drunken attempt to intimidate, or show his 'manhood'/toughness but with no intention of causing harm. Scaring people can make you feel powerful and Im sure Lynn liked feeling powerful. Perhaps he felt like it would 'teach them a lesson' for threatening him when they saw him with his BIG gun.
Talking to someone angry and very intoxicated while you're calm and sober often goes 1 of 2 ways.
Either Russell kept calm and sensible for some time, but at some point has got fed up with repeating himself because talking to someone extremely intoxicated is like talking to a brick wall and having judged Lynn as all bark no bite has told him to F Off back to his campsite, which lead to Lynn feeling like he had to remind Russell he was Billy Badass in this campsite so fired shots in the air, that's alarmed Russell and he's gone to grab the gun.
or 2nd way is Russell engaged passively, never escalated, but Lynn kept working himself up and up until he was enraged, stomping around and screaming, perhaps pacing back and forth, venting all his frustration and how better to vent rage than to shoot in the air, at that point Russell would understandably be very concerned and I could understand him making a grab for the weapon, or Russell has said something about Lynn firing shots in the air and Lynn got in his face to say 'what are you gonna do old man' and Russell was concerned enough to feel the need to try and disarm him.
There are a few reasons I think alcohol was likely a factor:
1 IIRC in one of the airline pilot forums soon after his arrest a couple of members talked about him drinking heavily.
2 He has been accused by previous partners and their family of domestic violence, while he was not convicted, the majority of domestic violence is linked with alcohol abuse by the perpetrator.
3 When he was arrested I remember them stating he had said things which concerned them and Lynn was talking about alcohol or getting drunk at camp.
4 I've spent 5 nights a week for years watching drunk people interact like this and Lynn almost perfectly fits the profile of a type who often behave as I described above.
If anyone can remember that airline forum would be great. It had some kind of weird name. With a 9 in it?