I felt that the white truck in the distance was an excuse to say I am busy...
Whether or not, we are not sure.
Notice how Jack didn't want to let go of the "greeting hug", Ennis thought it was too long, took his arms off.
Its a sign of bad news ahead. You know when a guy comes up with lots of excuses, he keeps looking for words haltingly and points at anything lame...
Of course Jack was devasted. So is Ennis. He stood there downcast and miserable. He didn't have to do it, he could have brought the girls along with Jack, (what's wrong with that??), somehow his paranoia kicks in and pushes Jack away. :'(