He also wrote about the death that same year for CNN, where he is anchor of the show, "Anderson Cooper 360", using his mother's words to describe the way Carter sat then clung to the balcony for a moment, then swung "just like a gymnast."
"I try not to imagine him hanging from the ledge," he writes. "Try not to imagine him falling. Did a couple out for an evening stroll catch a glimpse of him before he let go? Did a family gathered around the dinner table see him plunge past their window?"
"That's the thing about suicide," he writes. "Try as you might to remember how a person lived his life, you always end up thinking about how he ended it."
For years after his brother's death, Cooper writes, "I rarely say his name out loud anymore."
Suicide experts hailed Monday night's open discussion as important for both survivors of suicide and its victims.
Calhoun said the public discussion of such a private death, "shows a combination of strength and the desire to have this difficult set of circumstances be helpful to others facing similar kinds of valleys of the shadow."
"When you think you have the loss of a beloved child -- he chose to end his life and I saw him do it," said Calhoun. "And I was there and I did not have the superhuman capacity to prevent it. That is a combination of poisons [that] I think would take down just about anybody.
"The fact that Miss Vanderbilt has resilience and courage to still keep living and to talk about it is remarkable."
John Draper, executive director of TThe National Suicide Prevention Lifeline agreed that it was "brave" for mother and son to open old wounds.
"A lot of people don't want to talk about their pain," he said. "There is a lot of stigma talking about it. It took courage and strength to bare their souls in front of others and, in fact, help others."
The organization's online Lifeline Gallery features more than hundreds of personal stories from families who have mourned loved ones to those who contemplated suicide, then were inspired to seek help.
Hearing about the pain of losing a loved one can have a "profound preventive effect," said Draper.
"People who are in the throes of suicidal thinking are so caught in their own pain and wish for it to end," he said. "Often they believe they others are better off without them and a burden to others."
As Cooper and Vanderbilt share their grief, those contemplating suicide can see the "legacy of pain" that survivors carry, often through generations, said Draper.
But when those who consider suicide hear the pain loved ones like Cooper and Vanderbilt feel, "it's often it's a revelation to fully confront and realize that others suffer so much when they are gone."
If you, or someone you know, is in suicidal crisis or emotional distress call 1-800-273-TALK (8255) or go to the National Suicide Prevention Lifeline.