While she declined to share how Zack died, she said he left a message for his family. "His goodbye note did not mention sadness, anger, angst or depression, just a pressing madness about feeling like this world was not his home," Luke told PEOPLE of her son's death on Oct. 3.
The mom of 13 remembers her late son as an active, accident-prone boy. "He was my wild child; 13 broken bones, umpteen trips to the hospital with appendicitis, tonsillitis, a fractured skull. He was wild but so so so sweet," she said of Zack, one of her three biological children (the others were welcomed through adoption).
And much like his mother, Zack was known to be a compassionate friend and advice-giver to those in need.
"He was a faithful friend to the outcast and the troubled. Dozens of his friends have written to me and told me he was like a counselor to them," Luke said.
After his death, one of his friend's mom shared that "he saved her daughter's life when she was battling depression and anorexia, insisting the girl tell her folks and going with her to do that."
Her son's connection to those battling tough issues likely stemmed from his own battle with depression, which developed following a car accident in December 2016.
Zack fell behind in school after the accident, a rough breakup and an illness, then he learned he wouldn't be able to graduate alongside his classmates. Luke says "he was honest about [his depression]" and they sought help from doctors, a counselor and peer supporters.
In recent months, the radio host says her son was doing well, working to finish high school and begin film school.
While Luke and her family cope with the loss of Zack, she announced she'll be taking a break from her radio show and social media.
During her absence, "we'll be playing some of my favorite shows from the recent past. I'll look forward to my return, as you all lift me up so very much," she wrote in a Facebook post sharing the news of her son's death.
"Please pray for my beloved Zacky, and I will pray for all suffering from this debilitating disease called depression," she added.
Unfortunately, this is not her first child who has preceded Luke in death. In 2012, the family lost 16-year-old son Sammy to complications from sickle cell anemia.
Photo credit: Delilah