Clearly, you agree that that is impossible since you felt it necessary to have physical contact with your children at all times.
Yet, you cannot respond whether or not it is possible that the mother turned her head away for a moment when the mirror fell. Would the child have been safer if the mother had ahold of his hand? Certainly, well, unless they were both standing in front of the mirror.
My children were inclined to behave themselves. I didn't find it necessary to clutch them to me at all times. They survived. Most children do. This accident may have occurred because the mother was not watching her child closely enough. It may have occurred even though the mother was as vigilant as most people and the child behaving perfectly. We just don't know. I'm willing to admit that. Are you?
My littlest was in the cart. The boys walked beside it and had a hold of it. We talked. About everything under the sun. We laughed. We made fun of ridiculous items, style, color etc. They were never bored. They had my attention and knew it. Shopping was always secondary. They even helped shop and pointed out things as we walked the aisles.