First came the shots, then the police. Then they were told to hold each others hands and close their eyes. They didn't open them until they were outside. These memories won't go away anytime soon for these children.

Some kids saw the worst, like the 6-year-old who was in class when the gunman came in and shot the teacher. Others hid in closets, holding their breath until the killer passed by.

"The one thing to remember is that while these experiences are life-changing and traumatic, it doesn't mean these kids are damaged for the rest of their lives," said Dr. David Schonfeld, a childhood trauma expert who counseled city kids after 9/11.

After these types of incidents, counselors often focus on two stages of recovery: the immediate response of helping people feel safe and the longer-term process of helping them cope. Most people eventually heal, but between 8 percent and 15 percent are likely to develop post-traumatic stress disorder, according to Russell T. Jones, a professor of psychology at Virginia Tech who counseled survivors of that mass shooting.

Post-traumatic stress disorder, or PTSD, is a mental health disorder that can affect children and adults who have survived a traumatic experience. Children with PTSD typically experience three types of symptoms: re-experiencing the trauma, avoidance and increased agitation.

Dr. Melissa Brymer, director of terrorism and disaster programs with the National Center for Child Traumatic Stress, explains that anxiety, stress, sleeplessness and even guilt following a traumatic event is normal and even expected.

We also visited with an elementary teacher in Sioux Falls, Shannon Rook. She had a message for parents:

Seek treatment for children dealing with mental health issues. You need to act.