According to the official website of the Gary Sinise Foundation, Mac was diagnosed with a rare form of cancer known as Chordoma in 2018. This type of cancer originates in the spine and affects only about 300 individuals in the United States annually. While 70% of patients can be cured through surgical removal of the tumor, the remaining 30% face the possibility of cancer recurrence.

Despite undergoing surgery to remove the tumor in 2018, Mac experienced a recurrence of the cancer in 2019. Gary shared, «This marked the beginning of a challenging and arduous journey that gradually took a toll on him.»

Throughout his illness, Mac continued to pursue his passion for music. A graduate of the USC Thornton School of Music, he made the courageous decision in 2023 to complete a song he had begun during his college years. Despite being confined to his hospital bed and paralyzed from the chest down, Mac finished the song, titled «Arctic Circles,» using an iPad.

The completion of «Arctic Circles» inspired the creation of an entire album titled «Resurrection & Revival.» Tragically, Mac passed away the same week the album was scheduled for release.

On December 30, 2023, Gary rushed Mac to the emergency room as he struggled to breathe. Regrettably, Mac did not return home. Gary shared, «On January 5th, surrounded by his family, he peacefully let go. His battle with Chordoma was finally over.»

Gary described his family as «heartbroken» by the loss of their son. He expressed, «As parents, it is an unimaginable pain to lose a child. Our hearts go out to all those who have experienced a similar loss, and to anyone who has lost a loved one.»

He continued, «Our family’s fight against cancer lasted for 5 ½ years, and it became increasingly challenging as time went on. While we are devastated by his absence, we take comfort in knowing that Mac is no longer suffering. We are also inspired and moved by his unwavering determination throughout his battle. He fought against a cancer with no cure, but he never gave up.