Lacy Love, Ennis thought from the first that Jack had been beaten to death with a tire iron, just like the old man he saw as a child. Deep, deep impression that made. He knew too that Lureen wasn't totally straight with him, she seemed to be holding something back. If you were living in homophobic Texas or Wyoming or wherever back in the mid-Eighties, like Ennis, you could easily connect the dots in your own mind. A married man having an affair with a neighbour, who is also married, and he has made it known he wants to divorce his wife and take new man to meet Mama and Daddy, you bet it ain't gonna be pretty. Ennis just assumed that Lurren, who he thought was lying, must have known something about Jack's plans.
Whether Ennis was right or not we will never know. Annie Proulx doesn't even know. But that's what his gut reaction is. I mean the rim blowing off the truck may have happened once or twice, but what we have here is a man who sleeps with other men in a very violent, macho culture who put it about all during his rodeo days (witness the rodeo clown telling his mates the "faggot" has made a move on him! Childress is small, folks know everybody else. Two men getting it on, what's the chances no one suspected or saw something. Ennis isn't stupid. Hope that helps! Makes me sad that their story had to end that way, but there it is. Titus.