I wonder if the rifle was an older Remington Model 700 with the Walker trigger. They will discharge when opening or closing the bolt or releasing the safety on occasion without a trigger pull. Remington received 5 reports a week for 28 years on average of it happening.
I use shooting sticks, rest against a tree or sit down and put my elbows on my knees. I lay down and use my pack as a rest if the snow is not to deep sometimes too.