When we see someone physically or emotionally abusing a child, we want to intervene, but aren't sure how to do so. We sense that expressing our outrage will only aggravate the situation. To help, remember the acronym:

Distract
Ask a question, make a comment, drop something - anything to interrupt the anger and give the adult a moment to calm down.

Empathize
People who abuse their children are often deeply ashamed and see the child's misbehavior as evidence that they are bad parents. Make a comment that expresses your understanding of their frustration, for example, "It's hard to shop with little ones, isn't it?"

Model
Interact with the child in a more appropriate way, but one that supports the parent. The goal here is to teach by example, to give the parent a wider choice of behaviors toward the child. For example, distract a very young child, talk to an older child about the consequences of her actions.

Organize
Volunteer to provide respite care to high risk parents, set up a childcare co-op in your neighborhood, encourage parenting classes in your neighborhood schools.

In more serious situations, call Child Protective Serivces. If you have doubts about whether you should report, call them. They can help with the determination.