My first interpretation of the film was Jack died in a accident. Jack was allways a fuck up, i mean he never could do anything right. He could rodeo, he couldn't please his father, he couldn't work out how to pee when he was younger. He couldn't make a marriage work, he couldn't get another guy. Most importantly he couldn't have Ennis the way he wanted him. They only thing Jack Succeeded in was bringing Ennis from the dark. To only lose him again.....
His explained the accident like she was telling a story of someones death, at first no emotion.
How can blame her for being bitter, cold and harsh. She married a fuck up. A men that loved another man. Which she never found put about. So all she has in the world was business, a son that was a fuck up like his dad.
She was telling a men she had heard a lot about the way her husband dies. A men that was selfish enough to take her husband away, a men that never came to Jack. She would have loathed this men. But.......
She realises that Ennis Del Mar is more than a friend. She realises this by the way he talks, The emotion he shares with her over the phone. If you listen to just Ennis talking. Its amazing what you hear?

The accident it self is hard to believe,
Impossible No wayThan theres the Murder scenarioEnnis feared his whole life, He lived in fear. Fear drove him. It controlled. The news of Jack brings on these images because thats what happens to country gay men. Ennis leaned this at a young age. Thats when the fear began.
So first, Ennis hearing this unbelievable story with Jack's wife being so cold. This causes Ennis to have these first images. Why?
Thats what he believes, Thats all he knows happens to Gay men. The tire iron.........
Then when Ennis sees Jacks "Life" this unravels a side to Jack, Ennis feared. He wasn't Jealous as much of he feared Jack sleeping with Mexico boys.
But when he hears about this new fella, he realises that Jack had made a stupid mistake that Ennis tried to warn him about. Ennis knew this and so did we.
As much as i wish it was a accident,
I think Jack was murdered