Why is so scared the owner of the truck?
The owner of the truck is really scared while he's talking to Andy. Why he can't tell him the whole story at that moment? Actually, he asks Andy to get out of there. Maybe is he waiting for someone? Richard Horne?
Later, when Andy is waiting for him at the logging road we can see a shot of the house of this man with the door open. I supposse there's someone inside and maybe he attacked the guy
Well, the truck owner's acting and body language clearly implied (to me, at least) that he was afraid that someone could arrive or even just pass by and see him talking with a cop - so I assumed he was either scared of Richard Horne or some of his associates or both.
When he is late at the appointment with Andy and the camera I made the same assumption: either someone went in and attacked/killed the guy or, anyway, something bad happened (the shot is clearly edited to be ominous).
As far as I am concerned, it's pretty clear cut visual storytelling: "guy is afraid something bad may happen --> something bad happens".
I have the fury of my own momentum
The truck looked like the same truck Richard Horne was driving when he killed the young boy. That's what I believe Andy was questioning him about. "Who was driving that vehicle?" As to why the man was afraid? I believe it probably has something to do with Richard Horne and Red. I'd probably be afraid of those two sociopaths as well.
Also, does anyone else think that the house in that scene looks similar to Dead Dog Farm?
The truck looked like the same truck Richard Horne was driving when he killed the young boy.
It was the same truck; that lady who is a huge fan of the RR Diner (or any of the other dozens of onlookers) probably caught the license plate of the truck as it passed and reported it, and that's why Andy was there.
The fact that the truck belonged to the guy Andy was questioning, and not Richard, is interesting. Makes me wonder if he's working for Richard (given Richard's a Horne and therefore probably also rich), and that's why he's trying so desperately to shoo Andy away. Richard was using the truck to get illegal drugs as well, which also indicates that Richard's underlings (if this guy is one) are expendable to him.
I assumed that the guy asked Andy for two hours so that he could bolt out of town. When I saw the open door I took that as confirmation of it. It would be really, really dumb for a law enforcement officer not to detain the owner of a vehicle that was involved in a hit and run fatality, for exactly that reason.
Side question about that scene; where did Andy get a Rolex?