As a firearm-injury-prevention researcher and emergency physician, I learned early in my career to be clearheaded in a crisis. I use data, even in the face of horror, to provide actionable hope.Even so, the December 13 shooting at Brown University has been remarkably difficult for me to navigate. I know the Brown community intimately, having spent most of my career there. The people who were present are not abstractions. They are my friends, my mentees, my former students, my friends’ kids. The first responders, doctors, and nurses were my longtime colleagues. I am heartbroken, in a particularly personal way.After the lockdown alert was sent out, my cellphone quickly lit up with questions: What happened? To whom? Who is safe? Who has been reunited? The most frequent query, though, was: What can we do? Between the lines, people were asking for hope.Hope and facts are difficult to provide in the face of a tragedy so recent and so close to home. But if I have learned anything from my work, it is that hope is created through small, persistent action.The first thing we must do is grieve, with unabashed, full-throated, human sadness. We will mourn the two students who were killed. May their memories be a blessing. We will lament the forever-changed lives of the nine students who were injured, and hold their families in our heart. We will also grieve for those who were not shot, but who are nonetheless permanently altered by this tragedy.[Read: America is failings its children]The effects of mass shootings ripple out in concentric circles. So we must hold space for those who were present in the classroom, but not shot; for those who were in the building, or an adjacent one; for those who were elsewhere on campus, or who were in close-by buildings, and who remained on lockdown for hours; for the family and friends of faculty, students, and staff; for the first responders, law-enforcement officers, doctors, nurses, and techs, each of whom had to witness the unthinkable. And we must also think of the professors and staff and elected officials who had hoped to never have to confront the unthinkable.These groups are all more likely to experience PTSD, depression, anxiety, increased rates of substance use, and headaches than they were before Saturday’s shooting.And we must grieve for those present Saturday who had previously been exposed to this American rite of passage—whether at another university or a high school, a place of worship in their hometown, at a bar or festival or theater. According to a recent survey, more than half of American adults have an immediate family member who has been threatened with a gun, has been shot, or has been present at a shooting.That anguish, and the heartache we feel, will be unpredictable and nonlinear, but giving it expression is a necessary first step.In parallel, we can begin to try to make sense of what happened.We do not know all the details behind Saturday’s attack. Authorities detained and then released a “person of interest,” and the hunt for the perpetrator continues.Still, the national data are revealing. About 100 firearm injuries in the United States last year occurred at a school (and most of those were at a university). These school shootings are sadly just a sliver of the trauma. Approximately 44,000 other people were killed, and approximately 120,000 people were injured, by a firearm last year alone.Most firearm deaths are suicides, while most of the injuries are due to community violence. Domestic violence and unintentional injury are less common, but still more frequent than school shootings. These various types of firearm injury are, of course, interconnected.The majority of firearm injuries and deaths are preceded by a personal crisis—a job loss, a breakup, an argument. Mental-health struggles and substance abuse are often linked to gun violence, particularly to firearm suicide, but a prior record of violence is even more common, particularly among perpetrators of mass shootings. We do not yet fully understand what radicalizes people to hurt others. Hatred and hopelessness undoubtedly play a role. But there is almost always a preceding sign.Almost all firearm injuries and deaths, across the United States, are caused by a handgun.Firearm injuries and deaths are, by and large, less common in states that have stricter laws around firearm purchasing, storage, and carriage—but they occur in red and blue states, rural and urban areas, alike. And no other high-income country has injury and death rates like ours. [Read: ‘There is nothing libertarian about attacking bereaved parents’]Rhode Island was—until Saturday—proud to be on the short list of states that had not had a mass school shooting. But 14 years after Sandy Hook, it would be naive to think any state can escape this uniquely American tragedy for long.Read: Ten years after Sandy Hook, here weThese facts matter because they ground us. Instead of spinning into anger or fear, people can take data-driven action. We can be both reactive and proactive.I can’t yet offer specific actions that, had they been taken, might have prevented Saturday’s tragedy. Nor can I promise a magic wand that will fix this painful, persistent epidemic tomorrow. But we know that there are strategies that have worked on an individual and community level, in places across this country; this is the essence of the public-health approach to this epidemic. Everyone agrees that this has to stop, and these interventions provide us a path forward.Indeed, when we layer these solutions on top of one another—youth-mentorship programs, programs that help teens recognize potential signs of violence, laws that allow temporary removal of guns from people at the highest risk, and more—they make a difference. The long-overdue appropriation of federal funds for firearm-injury prevention in 2020, and the Bipartisan Safer Communities Act in 2022, have helped drive America’s gun-death rates last year to their lowest level in five years.That said, even though Rhode Island had many proven protections in place and has one of the lowest gun-death rates in the nation, it was not enough to protect colleagues and students in Providence on Saturday.So: What next? Even as I grieve, I am also beginning to knit together some answers—for how we can provide support to one another, for what policies and practices might have made a difference, and for how other universities and workplaces and schools can respond. I will also continue to advocate, tirelessly, to ensure that both research is conducted and action is taken with and for our affected communities. Only through data can I provide better, more effective answers for the future.And I take inspiration from my colleague Nelba Marquez-Greene, mother of a child killed at Sandy Hook. By neither retreating into anger nor giving up in sadness, she writes, this work “is hope.”