See my post 73. I'm assuming that most parents are smart enough to control their kids. When mine got too big for the carts, they were either in the basket or holding the pocket of my jeans. The MINUTE they let go I knew it and they were back by my side where they belonged. As they got older, when Hubby was along, he'd say, "where do your hands belong?". My boys put their hands in their pockets and stayed beside us.
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?