Christian rapper TobyMac is paying tribute to his late son, Truett Foster McKeehan, with a new song. On Friday (Jan. 10), the artist released "21 Years," a nod to Truett's age when he died in October.

"What started out as getting some of my thoughts and feelings about losing my firstborn son down on paper, ended up a song ... I never wanted to write," TobyMac (whose legal name is Kevin Michael McKeehan) explains on social media (quote via People).

"Until something in life hits you this hard, you never know how you will handle it. I am thankful that I have been surrounded by love, starting with God’s and extending to community near and far that have walked with us and carried us everyday," TobyMac adds on Instagram. "Writing this song felt like an honest confession of the questions, pain, anger, doubt, mercy and promise that describes the journey I’m probably only beginning. One thing I know is that I am not alone. God didn’t promise us a life of no pain or even tragic death, but He did promise He would never leave us or forsake us. And I’m holding dearly to that promise for my son as well as myself."

Truett Foster McKeehan died suddenly and unexpectedly on Oct. 23, at the family's Nashville-area home, after going into cardiac arrest. Like his father, Truett was an aspiring rapper, who performed as TRU, Shiloh and Truett Foster.

"He was a magnetic son and brother and friend," TobyMac said of his son in a statement following his death. "His smile, his laugh, the encouragement he offered with words or even without. He had an untamable grand personality and dreams to match."

“Truett always had a soft spot for God. The Bible moved him. His heart was warm to the things of his King,” TobyMac adds, reflecting on his son's faith. “He was by no means a cookie-cutter Christian, but give me a believer who fights to keep believing."

Formerly a member of Christian rap-rock trio DC Talk, TobyMac has been working as a solo artist since 2001. He is also a published author, the head of Gotee Records and the founder of Camp Electric, a music-focused camp near Nashville. In addition to Truett, TobyMac and his wife Amanda have four other children.

These Country Singers Know the Pain of Losing a Child

More From KLAW-FM