Gary Sinise's son, McCanna "Mac" Sinise has died from a rare form of cancer. He was 33.

The Gary Sinise Foundation shared the news on Instagram of Sinise's death on Tuesday, with the caption, "In Honor & Memory of McCanna ‘Mac’ Sinise 1990-2024."

Gary and his son, Mac Sinise. Gary's son died after a battle with a rare form of cancer. (Gary Sinise Foundation)

In a statement, the foundation said that on August 8, 2014, Mac was diagnosed with a very rare cancer called Chordom.

The foundation said that Chordom is cancer that originates in the spine and only affects an average of 300 people in the U.S. per year.