Difficulty sleeping. Bad dreams. Stomachaches, change in appetite, feeling jumpy or irritable. These are all normal reactions after going through a traumatic event like the shooting at a Morgan State University homecoming celebration Tuesday night.

School psychologists and crisis response researchers now have more than two decades of experience responding to school and campus shootings. Since the 1999 mass shooting at Columbine High School in Colorado, more than 338,000 students in the U.S. have experienced gun violence at school. At colleges and universities, at least 99 people have been killed in 12 mass shootings since the 1960s, and gun violence has injured or killed hundreds more. Mental health professionals now have a better idea how to help survivors and community members whose mental health may suffer.

“We’ve learned a lot over the years and unfortunately have gotten a lot of practice,” said Franci Crepeau-Hobson, professor of school psychology at the University of Colorado Denver and chair of the National Association of School Psychologists’ School Safety and Crisis Response Committee.

She said the good news is, “maybe surprisingly, recovery is the norm.” Symptoms like sleepless nights often dissipate in seven to 10 days. If someone who experienced trauma is still struggling after about two weeks, or if symptoms interfere with day-to-day functioning — which could show up as fear of leaving the house, sleeping with a weapon, thinking about hurting oneself or others, or frequent “checking out” or dissociating — they should pursue additional support, she said.

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Nadine Finigan-Carr is the executive director of the Center for Violence Prevention at the University of Maryland, Baltimore, which aims to address violence like the kind experienced by students and staff at Morgan State University. She also lives across the street from the campus and her son is a student.

So the response to the trauma to the campus and the wider community is “both personal and professional,” she said. ”The shooting was an extremely frightening experience, and for the next few days, weeks and months, it could be stressful for some students, staff and neighbors,” she said. “It may take longer to cope for some than others.”

She said it’s essential for everyone in the larger community — the Morgan Mile, as she said the area is affectionately known — to recognize they suffered a trauma even if they were not at the event and didn’t witness violence directly.

They should make sure they get rest, get proper nutrition and seek mental health services if they don’t feel normal, no matter what form that takes. Some people may be jumpy at the constant helicopters overhead or upset at the lack of resolution to the crime.

People should be allowed to be social if they need, and alone to “take a break” if they need.

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Some may also feel normal immediately and then not normal days later.

”The situation is unfolding,” she said. “There will be changes to the information as we learn more, and rumors and misinformation that gets spread and can cause more anxiety. This is a mass trauma.”

In the long run, she said schools and college campuses across the nation need to address the issues causing trauma in young people upstream so they don’t manifest into more violence.

”We know this is something that can be prevented if we apply community-based strategies,” she said. “We will work with the community, and not just tell the community what to do to reduce the tide of violence and gun violence specifically.”

Recognizing that trauma is at the root of much of the violence is key, said Freedom Jones, director of community violence for the LifeBridge Health Center for Hope, which works directly with people who have experienced trauma.

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”The perpetrators of violence have trauma,” she said. “People argue perpetrators are not victims. But it’s not normal to shoot and kill each other.”

She said that those who do not seek assistance when they experience trauma of any kind can go on to perpetuate the cycle. That’s why it will be essential for anyone on or around Morgan’s campus to seek mental health care when they need it.

The Center for Hope partners with Baltimore’s Safe Streets program, which involves “violence interrupters” who mediate disputes. That program has deployed workers to Morgan’s campus to assess the needs and ensure there is not more violence.

”There is trauma in running, there is trauma in standing there, there is just trauma and people need to recognize the impact of hearing about a shooting,” she said. “It penetrates our spirit and gets inside our bodies and our thoughts. That secondary trauma affects us all.”

It’s especially jarring for young people, who may have felt invincible or always safe before. ”We need to address this immediately and down the road,” she said. “The trauma can be like high blood pressure, a silent killer.”

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Crepeau-Hobson said facts help people and communities start to move past trauma, and this is more difficult when much is still unknown, such as the identity of the shooters and why and how they were able to do what they did.

The university should share information about the investigation “as soon as they get it” from law enforcement, and also keep the school community informed on what they’re doing to address safety, both physical and psychological — whether it’s increasing security, changing how events are held, or addressing mental health, Crepeau-Hobson said.

She said Morgan State should also provide information on common reactions people may have and when to seek additional help. Having conversations or “debriefing” in groups or in a town hall setting can be helpful as well, she said, but caution should be taken in groups to make sure members had similar proximity to the shooting, in order to avoid vicarious traumatization.

For example, someone who witnessed a person getting shot and needs to process it can inadvertently traumatize someone else in the group with more limited exposure.

Restarting classes as soon as possible will help foster recovery, too, Crepeau-Hobson said, and a sense of “they [the shooters] didn’t win,” she said.

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”When something like this happens, it makes us feel really helpless — because we are, right?” Crepeau-Hobson said. That’s why some shooting survivors engage in advocacy or policymaking, she said, “to gain back that sense of control.” Getting involved in making change “can be really empowering and can foster recovery,” she said.

In the end, Crepeau-Hobson said, “we’re not gonna respond to everybody the same way because not everybody’s gonna have the same needs.”