"Hunters in the Snow" -Motivation

"Hunters in the Snow"
by Tobias Wolff

The biggest question I had when reading this story was, "Why the heck are they doing these things?"  Why would Kenny almost run Tub over with his truck?  Why wouldn't Frank and  Kenny help Tub through the fences?  Why did Kenny shoot the dog?  Why did Tub shoot Kenny?  Why would Frank and Tub stop for a break twice while their friend was bleeding out in the back of a freezing cold truck?
So many questions and I can only give answers to two of them.  They connect, and I believe there is some irony involved as well.  The two questions that can be answered, at least partially, are why did Kenny shoot the dog, and why did Tub shoot Kenny?
As the three men are coming back to the house from hunting on the farmer's land, Kenny says that he hates a post, and he shoots it.  Then Kenny said, "I hate that tree," and shot the tree.  Then he looks at the dog and says, "I hate that dog."  Tub was completely amazed that Kenny shot the dog- "'What did he ever do to you?' Tub asked. 'He was just barking'" (Wolff, 192).  At this point in the story, it seemed to everyone, the characters and the reader, that Kenny had no legitimate reason for shooting the dog.  Its astounding to think that Kenny would shoot the dog just because he didn't like it or it was barking.
Tub was scared and confused and Kenny turned to him.  "I hate you."  Tub immediately responded and reacted by shooting Kenny in the stomach.  Tub's motivation seemed simple- "He was going to shoot me but I shot him first" (Wolff, 193).  Kenny said he hated things, then shot them.  When Kenny said he hated Tub, Tub thought Kenny was going to shoot him.  It seems slightly reasonable, but the men are friends, so Tub shouldn't have automatically assumed that Kenny was going to shoot him.  And Tub's reasons for his reaction is where the irony comes in.  Kenny said he hated the dog, and shot it.  Tub thought Kenny shot the dog because he hated it, and would shoot Tub because Kenny hated Tub.  But Tub and the reader soon learn the real reason Kenny shot the dog.  "'You asked him to?' Tub said. 'You asked him to shoot your dog?'" (Wolff, 194).  The dog was old and dying, and the owner didn't have a gun and loved the dog too much anyway.  Kenny was doing the old man a favor.  The whole basis for Tub shooting Kenny is gone.
Though those two actions have some motivation, all the other actions seem to lack true motivation, and that adds to the mystery of the story and the characterization of the characters- as emotionally messed-up, selfish bullies .