During a trip to Disney's Magic Kingdom, Robert Leibowitz wore a T-shirt asking for a kidney donor

Robert Leibowitz never expected that a family trip to Disney’s Magic Kingdom would change his life.

The 60-year-old New Jersey man has suffered from chronic kidney disease for decades and has been in need of a transplant. So, when he went to the Florida theme park in August, he was sure to wear a white T-shirt that read: “In Need Of Kidney O Positive Call 917-597-2651.”

While they were walking around the park, a woman, Rocio Sandoval, came up to them and asked if she could take a picture of his shirt, which she then posted on Facebook.

“Her picture just blew up! When we were boarding the plane, it was at, like, 40,000 [shares.] That’s when the calls started coming in,’ Leibowitz’s son, Max, tells PEOPLE.

Social media users from across the country saw the photo and began calling Leibowitz, offering to donate one of their kidneys to the stranger.

Credit: Rocio Sandoval

“It was insane how rapidly it was growing,” Max, 17, says. “When that picture went up and he started getting call after call after call, we were in shock. We couldn’t believe it. I didn’t know what to say.”

Robert Leibowitz (left) with donor Richie Sully
| Credit: Courtesy Max Leibowitz

From the dozens of calls, five people were tested to see if they could safely donate a kidney to Leibowitz. In the end, Richie Sully, of Indiana, proved to be the perfect match.

“I was in shock and I broke down in tears and I didn’t say a word for like 45 seconds,” Max tells PEOPLE of the moment he first got the news last week. “I was like, ‘Oh my God! It’s over.’ All the worrying about whether he’s gonna be able to go to my high school graduation or not is just all gone.”

Robert Leibowitz
| Credit: Courtesy Max Leibowitz

He adds: “It’s just a miracle. It’s unreal.”

Leibowitz told WFTV that he and his daughter came up with the idea for the shirt, and knew that wearing it to the famous theme park would help to get a lot of exposure. Sully told the station that he saw the post on Facebook and traveled several hours from Indiana to get tested.

“Fortunately, I am fairly healthy and I saw this as just another way to help someone out,” Sully said. “It just happens to require surgery.”

Leibowitz told the station earlier this week that he is still in shock over the news.

“I am a single dad,” he said. “I love [my kids] more than anything in the world and they are my rocket fuel. That’s what keeps me going.”

Now, Max says the entire family is looking forward to Leibowitz’s fresh start. And the family, along with Sully and Sandoval, have big plans for after the procedure.

“After the transplant, we’re all gonna try to go to Disney together,” he tells PEOPLE. “That’s where the magic really happened.”