School shootings such as the one at Sandy Hook Elementary in Newtown, Connecticut, may have long-lasting consequences, but with proper support, many children are able to move on, experts say.

Children need to be with their families as quickly as possible after exposure to such horrific events, said Steven Marans, director of the National Center for Children Exposed to Violence/Childhood Violent Trauma Center at Yale University's Child Study Center.

Marans and colleagues are making themselves available to Connecticut officials, including the governor's office and state police.

The good news is that most kids do bounce back from a single incident of trauma, said James Garbarino, professor of psychology at Loyola University Chicago and author of "Lost Boys: Why Our Sons Turn Violent and How We Can Save Them." If children can get back into their normal routines and get proper support, he said, they will do well.

Declan Procaccini, father of a third-grade student at Sandy Hook, told CNN's Wolf Blitzer his daughter was in a reading class on Friday when she and a teacher "heard bangs." The teacher locked his daughter and another teacher in a bathroom until police escorted them out through a messy scene.

"I don't know if my daughter's in shock or not, but from what she told me she saw, she's doing incredibly well," Procaccini said.

Procaccini's 10-year-old son is also doing well, he said, but there are still fears of a repeat incident.

"My kids are already asking, 'When is this going to happen again?' It was only a week ago that we were talking about this type of situation, and I said the chances of it happening are one in a zillion at Sandy Hook. I was wrong about that."

Long-term issues are more likely for children who were very close to someone who died in a shooting, who witnessed the event or who were in close physical proximity to it, Garbarino said.

In addition, "Kids who are having difficult lives before the event are the ones most likely to have issues," Garbarino said.

For instance, if a child's parents are going through a divorce or if the child had been fighting with a parent on the day of the event, he or she may feel more of an impact from a traumatic event such as a school shooting, he said.

Moreover, if a child is frequently exposed to violence, such as by living in an abusive household or a dangerous neighborhood, a school shooting may add to existing trauma that child has stored up, Garbarino said. In those situations, it's hard to lean on the idea of "going back to normal."

There is evidence that elementary-school children are particularly vulnerable to trauma, more so than teenagers or adults, Garbarino said. This may be because although these children have enough awareness of a situation to appreciate danger, their brains and bodies haven't matured to manage the effects in the way teenagers and adults can.

Symptoms

Trauma from a school shooting can manifest itself in physical ways, such as stomachaches, headaches and sleeping difficulties, said Nancy Rodda, senior director of clinical services for Genesee County Community Mental Health in Flint, Michigan. In Rodda's county, a 6-year-old boy shot a 6-year-old girl to death at an elementary school in 2000.

Stress can instigate a variety of behaviors: For instance, anxiety can lead to poor eating, which can lead to stomach discomfort, Rodda said.

Alexis Wassick, a student at Sandy Hook Elementary, said Friday that "people were even like, they kind of got a stomachache."

Kids may start depending on their parents for things they're normally able to do on their own, Marans said. They may also become more irritable.

It's not only a single event that puts children at risk for developing long-term mental health problems such as post-traumatic stress disorder, anxiety and depressive disorders, Marans said. How well they were doing before a school shooting will have a big impact.

There also is the issue of survivor's guilt, Rodda said. Children who have lost friends may wonder why they themselves lived.

Support

One of the best predictors for good outcomes is when kids have adequate support from their families and communities, Marans said.

Parents should listen to their children, reassure them that they are safe and look out for any changes in behavior, Rodda said. Let children ask questions, and don't force anything on them, Garbarino said.

"There's a balance between talking about it but also not dwelling on it too much," Rodda said. "Overexposure can increase stress."

Procaccini said he's been talking to his children, explaining what happened. "You do your best to communicate with them," he said.