Public violence and recent tragedy, including the deaths of Charlie Kirk and Iryna Zarutska, have left many shaken by what they have seen.For witnesses, whether seeing the event in person or on a screen, these memories can be difficult to shake, potentially developing into grief and trauma.Jonathan Alpert, a New York psychotherapist and author of the upcoming book "Therapy Nation," reflected on the common mental health effects of witnessing a traumatic event, such as a murder, in an interview with Fox News Digital.HOW TO COPE WITH COLLECTIVE GRIEF WHEN MASS TRAGEDY STRIKESThese effects may include shock, fear, hypervigilance, difficulty sleeping and a mental replaying of the images."These are normal short-term responses to something that feels overwhelming," Alpert said.Within the first hours and days following the event, reactions can also include numbness or disbelief, as if the event is "unreal."While some peoples emotions stabilize and symptoms fade over time, others may experience intrusive thoughts, nightmares or emotional detachment in the following weeks, according to the expert.LAWMAKERS CALL TO REMOVE CHARLIE KIRK ASSASSINATION VIDEOSThis may signal that the trauma is becoming "more entrenched," he said.For certain groups, such as college students still developing their sense of "identity and safety," an event such as Kirks death may leave them feeling "especially vulnerable.""They may associate with the event more strongly because it was on a college campus," he said. "Older adults may have more coping skills, but can also be triggered if the event stirs up earlier life traumas or deep anxieties about the state of society."The psychotherapist urged the public to keep an eye out for red flags that may signal the need for professional help, including someone's inability to function at work, school or home.CLICK HERE TO SIGN UP FOR OUR HEALTH NEWSLETTER"Persistent insomnia, panic attacks, irritability that strains relationships or withdrawal from daily life are signs that the stress response has gone beyond the normal range," Alpert cautioned.Some coping mechanisms include grounding techniques like deep breathing, writing down thoughts and feelings, and talking with trusted people."Even small routines, such as starting the day with a brief mindfulness exercise, can buffer against anxiety," Alpert said.Getting adequate sleep, exercising and eating healthy foods can all be beneficial. Physical activity, in particular, is known to release tension from the body and calm the nervous system."Setting boundaries around news and social media is also critical," Alpert said.Constant exposure to violent imagery on social media has made the public "numb" to events that 20 years ago were deemed "horrific," he added."It seems like there's a school shooting every other week now, and we barely acknowledge it," he said. "People become desensitized, and what was once considered a really bad crime is probably much easier to absorb now."The psychotherapist emphasized that "trauma isolates and connection helps."For more Health articles, visitfoxnews.com/health"Support from family, friends and faith communities provides a sense of belonging and safety that is essential for recovery," he said."Talking openly, sharing meals or engaging in spiritual practices can anchor people and remind them they are not alone."