After 9/11, how we honored our son's memory Patrick, a former child soldier, received treatment at a PCAF clinic and was able to care for his family. Elizabeth and Stephen Alderman: Our youngest son, Peter, was killed on 9/11 After his death, they knew they had to leave a mark that Peter existed They set up the Peter C. Alderman Foundation to help people affected by terrorism Elizabeth, Stephen Alderman: Peter would be proud of the work that bears his name Editor's note: Elizabeth and Stephen Alderman are the founders of the Peter C. Alderman Foundation. (CNN) -- Our youngest child, Peter, was murdered on September 11, 2001, while attending a conference at Windows on the World at the World Trade Center. He was 25 years old when he died. When the towers fell, we were in France, on vacation to celebrate Steve's 60th birthday. Peter, our daughter, Jane, and our son Jeff and his wife, Tobey, had all been with us for a week before flying back to the U.S. on September 8. On the day of the attacks, we were terribly upset after hearing the news. But at first, we were not worried about our kids. Jeff and Tobey lived in Tulsa. Jane lived in D.C. but her job was nowhere near the Pentagon. Peter worked in midtown Manhattan for Bloomberg LP. But since he traveled throughout the city for his job, we became concerned. Elizabeth and Stephen Alderman Peter Alderman We desperately tried calling our kids but could not get a line out of France. It wasn't until late in the day that we learned from Jeff that "Pete was there." The next day, Michael Bloomberg, who became mayor two months later, called to tell us that Pete was dead. My world stopped, and it still is totally out of kilter. Not Peter! Pete was all laughter and sunshine and love. He wasn't uncomfortable kissing his mother or father in public, or hugging his sister for no reason at all. He and Jeff traveled to fun places and laughed and laughed. Not Peter -- he was too full of life. Our mark on this Earth is our children. After his death, we knew we had to leave a mark that Peter existed and the world would be a better place because he lived. In searching for a way to honor his life, we learned that 1 billion people, almost one sixth of humanity, have directly experienced torture, terrorism or mass violence. Victims are left with lifelong emotional wounds preventing them from leading productive lives. In sub-Saharan Africa, the incidence of traumatic depression and PTSD exceeds that of HIV/AIDS, malaria and TB combined. Peter loved life; he was compassionate and caring. There was nothing we could do for Pete, but returning survivors to life in his name was the perfect memorial. In March 2003, we created the Peter C. Alderman Foundation. People often ask: "Why are you dealing with traumatic depression and PTSD when there are so many greater problems in the world?" Our response is simple: Billions of philanthropic dollars go into fighting HIV/AIDS, malaria and poverty. But if people don't care whether they live or die, they will not follow through with their medication regimens, walk that extra mile for potable water or take advantage of microfinance. If you can restore hope, a person is less likely to strap on dynamite and kill innocent people. Our foundation started by training indigenous health workers, but we quickly learned that training by itself was not sufficient. We needed to provide a framework in which professionals could work. To that end, our foundation runs eight trauma clinics in Cambodia, Uganda, Liberia and Kenya. Establishing public-private partnerships with local governments, our foundation trains, supervises and pays its staff; the government provides clinic space, in-patient beds and psychotropic drugs. Our foundation's average annual cost per clinic is $30,000. More than 30,000 children have been abducted in Uganda, and many of our patients are child soldiers, like Patrick. He has been treated in our Kitgum clinic for two years. Now he no longer has nightmares or flashbacks. He can sleep through the night and hold down a job. He no longer thinks of suicide. He has even named his new baby after his counselor at the clinic. Our foundation sponsors an annual African training conference on traumatic depression. At July's fifth annual conference in Tanzania, attended by 500 mental health professionals from 22 countries, an imam from Somalia rose to say the opening prayer. He only spoke Arabic. When translated, we learned that he had said a prayer for Peter. Tears streamed down my face as I realized we were truly on the way to leaving that mark for Peter. The work has kept us functioning and given us a reason to get out of bed every day. Nothing can erase our pain, but our passion to leave a profound and indelible mark that Peter existed on this Earth has propelled us forward. Peter would be very proud of the foundation that bears his name. The opinions expressed in this commentary are solely those of Elizabeth Alderman and Stephen Alderman.