Was George justified in what he did to Lennie at the end of the book or not?

knew the Ranch men were coming to lynch Lennie. Curley, in particular would not want to wait for a trial. Lennie's death would be terrifying and painful. If Lennie was taken alive, he would be locked up like an animal and as Slim had said, "that ain't no good". So, George really did not have much choice with the situation at hand. One has to agree that Lennie dreaming of his rabbits and then an instant death is a far better option than what probably would have been.

The first sentence shoud read "George knew the ranch men were coming to lynch Lennie."