and that is what safeties are for... and that is what safeties are for...The safety located at the trigger guard is of no use as far as a dog pulling the trigger. I had this very thing happen to me, and I was 15 yds away when I herd the dog drop the hammer.
I had left the blind to attend to the decoys. Laid the gun down and started out. Picked the gun back up and only jacked the shells out as an after thought.
The dog waited till I was in his sights, and stepped on the trigger guard. One toe clicked the safety off and another toe tripped the trigger. A very loud click followed.
It can happen, Labs can and do get into the strangest situations.