What should we have said—and say in the future—about an employee fired for theft?

Q. We fired a part-time employee for stealing a gift card out of the trash. We have a policy against taking anything of value out of the garbage. The next day, his supervisor announced to everyone that the employee had been fired for theft. I don’t think it was appropriate to tell others the reason. Was it? And what should we say if someone calls for a reference?