Then how did it end up so neatly and suggestively across her chest?
seriously do I have to explain this?
1. Person sits up with the rifle muzzle end on their neck and the stock end between their legs
2. With one hand by the trigger and the other hand round the barrel
3. Once they are dead or dying they will fall back, the rifle then goes down with the body due to gravity and partially directed by the individuals grip on the barrel but mainly due to gravity.