In the case of my neighbor he had ran saws his entire life, and even did some logging when he was younger. Being an gentleman in his upper 60's things can get missed, or sometimes the falling limb may not of even been evident and could of broke off another tree next to what he was cutting.
I have been running saws since I was 10, and sometimes things happen that were never expected even though you know it could be possible. Been cut on the left elbow after being thrown through the air while relieving tension on a small 2 inch diameter tree that I was expecting to splinter and flex up and away from me, not break off and hit me in the chest.
His son was supposed to come this weekend to help with the firewood cutting, but he insisted on getting started even though his wife tried to persuade him not to.