At the center of the human brain is a tiny almond-shaped organ, known as the amygdala, which triggers deep emotional responses, from fear and worry on the negative side to courage and caring on the positive side. This part of the brain, which we inherit from our animal forebears, cannot handle both sets of emotions at exactly the same time, which is why we can’t be both fearful and courageous at the same moment.

During the horrifying shooting at Sandy Hook Elementary School, last week, the children and their teachers experienced an amygdala-provoked fight-or-flight response, an outpouring of stress hormones (adrenaline and noradrenaline) that helped hundreds to escape. But over time, these hormones, together with the inability to regulate the steroid cortisol, might contribute to the development of post-traumatic stress disorder, characterized in adults by flashbacks, nightmares, anxiety, and dissociation and in children by rages and sadness while at play, and feelings of isolation and low self-esteem.

Studies of previous school shootings indicate that a very high percentage of survivors and their families will experience PTSD in the first one to two years after the tragedy, as will some of the children who live in the neighborhood or have friends who were killed. Luckily, there are effective treatments for PTSD. Cognitive-behavioral therapy, which centers on the event and helps people work through it, is very effective at helping survivors cope. Long-term studies on the 1999 Columbine shootings have not been done, but some survivors have had continued flashbacks and exhibited discomfort at viewing violence in the media.

What about the rest of us? Vicarious, or secondary, traumatic-stress disorder is a term meant to apply to families of victims or survivors, but it has also come to be used for people who watch hours upon hours of cable-news reports of the shootings. From Columbine to Virginia Tech to the movie-theater shooting in Aurora, Colo., to Sandy Hook, hours spent watching coverage can have a cumulative impact that may lead to a cycle of worry, anxiety, and sleeplessness.

The popularizing of PTSD in the media has led many who aren’t directly terrorized to use it as an explanation for their own escalating fear. But people who are afraid to send their children to school because they have watched reports of the Sandy Hook shootings are overpersonalizing the risks. “The mention of post-traumatic stress occurs because there is a shortage of terms for laypeople to use for their vulnerabilities when they’re confronted by trauma,” says Rachel Yehuda, PTSD expert at the Mt. Sinai School of Medicine, in New York City.

Nevertheless, the impact of a school shooting on obsessive TV-watchers is real even if not completely justified. According to research conducted by Elizabeth Phelps, psychologist and neuroscientist at NYU, viewing dangerous events can activate the brain’s fear mechanism as much as if the subject had experienced the danger herself.

Of course, it’s healthier if the public’s response to the shooting is sympathy and compassion rather than fear for our own children’s safety. School shootings are extremely rare, and they do not appear to be on the rise nationally. It may make some sense to beef up school security, and it definitely makes sense to advocate earlier intervention with mental illness and perhaps less gun availability in homes where the mentally ill live. But the expectation that our children’s school will be next is not realistic.

Even as we mourn, we need to distinguish victims, survivors, and their families from the rest of us — the concerned onlookers. This is not a national tragedy as much as it is a terrible personal tragedy for the parents who lost their young children to brutal murder. We can only imagine how that must feel.

— Marc Siegel, M.D., is an associate professor of medicine and medical director of Doctor Radio at NYU Langone Medical Center. He is the author of  False Alarm; the Truth About the Epidemic of Fear.