For example, in the given scenario, that the September 11th attacks on the United States altered the perceived need for a particular type of labor, to wit, security personnel, the relevant market shift is an increase in demand. Once the demand has increased, supply and demand are no longer balanced, and the market equilibrium is disrupted. To reset this balance, wage and the value of marginal production must also increase to the point where stability is again achieved. Simply put, and assuming that supply remains unchanged, the greater the demand for a particular type of labor, the greater the marginal value of a particular worker's product, and, thus, the greater must that worker's wage be to achieve market equilibrium.
It is logical that the September 11th attacks created a greater demand for security personnel. Society became much more concerned with creating safe environments at locales such as airports, in airplanes, at events where large amounts of people congregate, and at globally-recognized structures.