I find it unlikely that Boris was both the victim and the murderer.
No, I don’t think so. Thimbleweed Park doesn’t seem to me the kind of game that explicit tells you who the murderer is.
Nobody knows for sure but here is a very interesting thread about the many “theories” that have been created by some of us.
Anyway, the most popular line of thought is that Chuck was the person who wanted both Boris and Franklin to die.