Gary Sinise Tearfully Reflects on His Late Son Mac's Legacy: 'I'm Proud to Be His Dad' (Exclusive)

McCanna "Mac" Sinise died in January after battling cancer for more than five years. He was 33 years old.

Gary Sinise is opening up about his son's tragic death. Two months after McCanna "Mac" Sinise died following a more than five-year cancer battle, ET's Rachel Smith spoke to the Forrest Gump star about his son's life and legacy.

"He was a pure soul. He had a pure heart. He was a gentle, loving, kind, funny, talented guy," Gary told ET of Mac, who was 33 years old. "... He loved his family. He loved his sisters. They were so close. He loved his mom. She was constantly with him throughout this cancer fight."

When Gary shared news of Mac's death, he also revealed that his son was diagnosed with Chordoma in 2018, the same year his wife, Moira Sinise, discovered she had breast cancer. 

"There was a really stormy period where my dad had a stroke, and then my wife had multiple spine surgeries, and then she got diagnosed with cancer, and then my son got diagnosed with cancer a couple of months later," he recalled. "It was just like, 'God, what's going on? What's happening? This is challenging.'"

Through the actor's work with his Gary Sinise Foundation, which works to honor defenders, veterans, first responders, their families, and those in need, he saw "so many families go through really difficult things."

"I think some of that over the years, having seen so much of that, had prepared me well to just say, 'You can't let this paralyze you. You have to get in the fight,'" Gary said.

That fight began in 2018 when Mac's tailbone pain became too much to bear.

"He was a having a lot of pain in his tail bone. At one point years ago he kind of slammed on the breaks too hard on a bike and he jammed his tailbone, and we thought it had something to do with that," Gary said. "He'd say, 'I'm having a lot of pain here.' And then the pain got too much for him and I was like, 'What is going on here?'"

Eventually, Mac went to see a spine surgeon who discovered "a massive tumor on his sacrum."

"People can go for years just thinking they have a bruise there or something... then all of a sudden you discover you had a massive tumor growing there for years," Gary said. "This is the kind of slow-growing tumor that it could've been there since birth. We don't know."

While 70 percent of the time a tumor of that kind is able to be removed and the cancer is cured, 30 percent of the time it grows back, which is what happened to Mac. When, after Mac's September 2018 surgery, the cancer returned in May 2019, Mac was determined to continue his work with his dad's foundation, which he had been contributing to since his childhood.

"He grew up around it. He's an excellent drummer, started playing with my band, I would take him to military bases, he would play with us," Gary said. "... He admired what I was doing and cares about our veterans and all of that. Finally I roped him into coming to work for the foundation back in 2017. He started and he loved it."

Soon, though, "things were getting a little trickier" for Mac as he began having side effects from chemo, radiation and medication. That led Gary to put his own career on hold to care for his son.

"In early 2020, Mac was going to have to have another surgery on his spine, because there were more tumors growing on his spine. And then he had another surgery in June," Gary said. "So in 2020, I just pulled back and put all my attention, all my focus on trying to help him, while at the same time still trying to continue with the mission of the Gary Sinise Foundation."

"I just kept going and trying to do what I could and work with the doctors and try to take that away from Mac, so he wouldn't have to think about talking to doctors and talking about cancer all the time," he added. "... Because I had a solid career, I could afford to stop and to just be available to my son and my wife, who was also going through challenges. Thank God I could afford to do that and take time to focus on them, while at the same time trying to continue the foundation work."

Even as Mac "was getting more and more seriously ill," he remained determined to fight.

"It was not going to get better. There's no cure," Gary said. "We tried 25 different drugs. These are just drugs that are used on other cancers and the doctors kept trying and they said, 'As long as you want to keep trying, Mac, we'll keep trying. We'll come up with something.' Mac said, 'I want to keep trying.' He was an incredible fighter."

Eventually, Mac became paralyzed from the chest down, which was a "blessing" in some ways, Gary said.

"It was very painful and all of a sudden he couldn't feel anything from the chest down, so that pain that he was feeling before was gone now, but he couldn't walk," Gary said. "It's just the nature of this awful cancer. He was fighting and I wasn't going to stop fighting for him. I never wanted to think that we were going to lose the battle even though you know that you're fighting uphill all the way." 

As his health deteriorated, Mac decided to return to one of his first loves -- music. He taught himself how to play the harmonica at the suggestion of his mom, and was able complete his album, Mac Sinise: Resurrection and Revival, before he died.

"The last year of his life he started to create music again and it was beautiful," Gary said. "I bought him his first drum set when he was 9-years-old... He played through high school and then he went to USC Thornton School of Music. He was playing drums all through college and studying songwriting and composition. He created a bunch of pieces of music while he was at college. He just put them away and didn't do anything with them. About January of 2023, he said, 'Dad, I think I want to try to finish this music that I worked on all those years ago in college.'"

Gary recruited musicians from his band and Mac enlisted the help of a college buddy for the project.

"He achieved it. He got it all recorded. Him and his buddy Oliver worked so well together and created this beautiful music," Gary said. "The album, it's being pressed right now. It's in presale at the Gary Sinise Foundation right now... As soon as it's pressed we'll start releasing it. Eventually all of his music will be on the digital platforms and everything."

The album was completed in the final week of Mac's life.

"That last week, he finished the record. They had a viewing party... It was a joyful day," Gary recalled. "The following night, I went on television and talked about Mac. Then the next day, I had to call the ambulance and take him to the hospital."

Despite calling the ambulance, Gary was unprepared for what came next.

"Quite frankly, we'd been through this so many times, call the ambulance, go to the ER, get him stabilized, and come home. I thought that's what was going to happen. That's where my head was. I wasn't thinking that this was going to be the time," he said. "... It wasn't until the last couple of days that it became clear what was going on. But the first few days in the hospital, he was happy that he'd accomplished what he wanted. That's what I want people to know about... Mac never gave up. He kept fighting." 

Soon, though, "it got too tough" for Mac.

"It wasn't going to get better. It was going to get harder," Gary said. "He was at peace. He was happy at the end of his life. He was joyful... He was smiling." 

Gary even lovingly recalled one memorable moment from that hospital stay.

"I was staying with him at the hospital at the end... I had to step out for something at one point, and I stopped by the nurse's station on the way in. I said, 'How's Mac doing? What's he's doing?'" he said. "[The nurse said], 'He's watching Forrest Gump on his phone.' He was in there watching Forrest Gump. It made him feel good. I think it made him feel closer to me sometimes. He would watch it when I was gone."

In sharing his family's story, the CSI: New York actor hopes to shine a light on the legacy Mac left behind, though that's a difficult thing for him to wrap his head around at present.

"It's hard to even think like that, because somehow it feels like he's just on vacation, he's gonna come back," Gary said, before pointing to the discovery of his son's musical talent as something that has been filling his family "with joy" through the heartache.

Also, sharing Mac's journey was all about sharing who Mac was with the world.

"He inspired me, and if telling his story can inspire others to just persevere through their own challenges and never quit, never give up, never give up living, then that's a good thing. That's a reason to share it," he said. "... I'm proud. I'm proud to be his dad."

As for how he moves ahead, Gary admitted that that's "hard to say" right now.

"I know I want to keep helping people through the Gary Sinise Foundation. That has lifted me up. Throughout this challenging time with Mac, I was still trying to go out there and play concerts or visit the troops, do the work of the Gary Sinise Foundation. All that service work, that lifts you up. That helps you through your own stuff... It's still going to help me through," he said. "All that service work is going to help me through our own family challenges and our loss and our missing and the pain and the sorrow... I'll keep doing that as long as I can."



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