Tomorrow will mark the fourth anniversary of the tragedy at Sandy Hook Elementary School, when 26 students and teachers at the Newtown, Conn., school died in a gunman's attack. Sadly, Sandy Hook was not an isolated incident. K-12 schools in 12 states experienced an active threat event between 2000 and 2013.

And, of course, schools are not alone in their vulnerability. Institutions of higher education, private businesses, houses of worship, government offices and other public spaces, from San Bernardino, Calif., to Charleston, S.C., have experienced their own horrific mass-shooting incidents. The reality is that there are likely to be more of these kinds of attacks, and we need to be ready to deal with the aftermath of them.

In my experience as a former director of a state emergency management agency and my current role advising emergency managers across the country, I have seen firsthand the benefits of training and exercise efforts focusing on the initial-response phase of an attack. But while practicing response tactics is critical for first responders, there are many other consequences of an attack that require just as much attention. This includes the complex tasks related to reunification of survivors with their families and dealing with the needs of those who have lost loved ones.

Too few training and exercise programs involve planning and preparation for recovery efforts such as reunification in the aftermath of one of these tragic events. We need to expand our training and exercise investment to include all stakeholders, not just first responders.

While some planning has occurred related to locating and managing a reunification site, one of the biggest challenges officials face following one of these events is the need to rapidly collect information. We should be prepared to take advantage of the opportunity to harness crowdsourcing in the reunification process and include those processes in the planning effort.

With these considerations in mind, here are some strategies that ought to be integral to the reunification process:

• Prepare to manage a reunification site. Families, students and friends will experience varying emotions once they find out the fate of their loved ones. How is the reunification site designed to separate those who hear good news from those who hear nothing and those who hear the worst?

• Establish procedures to enable first responders to communicate accurate and timely information to the public. We saw news footage of students at Ohio State University using their phones during and following that recent attack. These attacks unfold quickly, often over less than 12 minutes. We can't beat the speed of social media, but we can harness it to help people recover from these events as quickly as possible. One source of information can be survivors. We can secure accurate information from first-person witnesses, aggregate it and disseminate it to responders and emergency managers to provide situational awareness before, during and after an attack.

To address these questions and develop the capabilities needed after a threat event, we need a three-phased approach that stresses planning, training and exercising. This approach requires stakeholders across a community to be involved. All of them play a role in recovering from an attack like the one that devastated Sandy Hook four years ago.