Ayden Zeigler-Kohler was diagnosed with incurable cancer when he was just nine years old. He and his family naturally vowed to fight the illness, but eventually the boy told his dad, “I gotta quit.”

When Bill Kohler’s nine-year-old son, Ayden, was diagnosed with terminal cancer, his entire world was turned upside down. Understandably, the brave boy and his dad refused to give up without a fight, and they held on for as long as they could. But when Ayden told him, “I gotta quit,” Bill realized that the struggle was over. And what the father said next was incredibly heartbreaking.

In August 2016 Ayden Zeigler-Kohler lived with his family in York, Pennsylvania, and was a regular nine-year-old boy. Like many young kids his age, for instance, Ayden was extremely active and loved to play football.

But one day that month, Ayden and his family’s lives changed in the blink of an eye. Indeed, the youngster had been at football practice when he suddenly collapsed. His parents consequently rushed him to a nearby hospital, and the doctors told them that their son had suffered a concussion.

However, in the days that followed, Ayden’s condition began to deteriorate. He was, in fact, losing his ability to speak and some of his motor skills. That’s when Ayden’s dad, Bill Kohler, first realized that something was potentially very wrong with his little boy.

And it turned out that Bill was right to worry. Indeed, doctors later discovered a tumor in Ayden’s brain that stretched from his brain stem to his cerebellum. They then diagnosed him with a rare form of cancer known as intrinsic pontine glioma.

Doctors also estimated that little Ayden had only up to one year to live. So now all his father could do was watch Ayden wither in front of his eyes. “He was so lethargic,” Bill told TODAY in March 2017. “I had to carry him everywhere. He couldn’t walk. He was losing motor function, constantly sleeping. The look in his eye was just a daze, like he wasn’t even there.”

Of course, Ayden had medical care to try to limit the pain; radiation treatment helped halt the illness. However, in the end, any positive effects would only be temporary. Understandably, it was a heartbreaking time for the family.

It was especially overwhelming for dad Bill, as Bill and Ayden had always been close. In fact, the doting dad credits the little boy with saving his life. That’s because prior to Ayden being born, Bill served in the Army for 17 years. And when he came home in 2006, the Iraq veteran struggled with depression and anxiety.

“I was isolated and started drinking pretty heavily,” Bill admitted to TODAY. “Nothing was going right for me… and then Ayden was born. I just threw myself into him. Once that happened, it was like a bunch of good things started happening. I finally got into the V.A., I started therapy.”

As a result, Bill refused to give up his hope for Ayden. He even committed himself to researching the rare form of cancer his son had. Furthermore, he inquired about clinical trials with the hope that a medical breakthrough might save the boy.

In the meantime, the family focused on squeezing as much life as they could in between doctor’s appointments and chemotherapy. Indeed, they worked towards creating cherished memories with Ayden by ticking off items on his bucket list.

And to help fund the little boy’s dreams, friends and loved ones donated almost $90,000. As a result, the family enjoyed fishing and hunting expeditions together. In fact, Ayden would spend as much time in nature as he could, as it was one of his most cherished places to be in.

One particularly poignant moment for the family came when the Pennsylvania Game Commission arranged for Ayden to visit some bear cubs. Since Ayden could no longer walk at that point, Bill carried him to the bears, who nuzzled the boy’s face and cuddled into him.

Ayden also enjoyed football and basketball games, and he even got to meet Pittsburgh Steelers player Ben Roethlisberger. Meanwhile, the Harlem Globetrotters and WWE offered the youngster tickets to future events.

However, Ayden would sadly never get to see the Harlem Globetrotters. In March 2017 his health took a turn for the worse. And robbed of the ability to walk and eat unaided, he finally told his heartbroken father, “Dad, I gotta quit.”

It was the moment that Bill had dreaded, but he knew his little boy had done all he could. “If you’ve fought as much as you can and as hard as you can and you feel you fought that hard, I promise you it’s okay to quit,” he told his son.

Little Ayden later died at home with his family present. It had been just seven months since his diagnosis, and the child was just ten years old. At the time, Bill had been preparing to talk on camera about his family’s heartache.

However, after hearing of his son’s passing, he abandoned his filming and forgot to turn off his microphone. Consequently, the device captured his final, heartbreaking conversation with his son. “I’m sorry that I couldn’t do more,” he whispered to his deceased baby boy.

“You wanted to be in a better place. Now you can go there. Go run again. Play again,” Bill urged his beloved child. “You’ve given me the purpose in my life. I won’t let you down. I love you, son.”

The battle for their son’s life was lost, but Ayden’s parents continue to fight for other children with the same condition. So while they may not have been able to save their beloved boy, they hope in the future that other parents will be spared the tragedy they’ve endured.