"It was one of those moments where you don't know how to act, you don't know how to react. I didn’t say anything." he explains in an emotional video that has now reached nearly 1 million people.
"I heard that voice in my head say, 'Tell them what it is,' and I didn’t. I let that ignorance grow in another generation and failed my son in the process," he continues.
"Down syndrome is literally one of the most beautiful things that's ever happened in my life," Scott says as his eyes well up with tears. "It's fun, it's brilliant, it's amazing, it's funny, it's kind, it's loving, it's cuddly. They're great teachers, people with Down syndrome. It's not an illness. It's not even a disability."
Because he wasn’t able to speak up in the moment, the father of two recorded a video about his experience moments later and shared it on Facebook.
"Down syndrome is the best thing that ever happened to me, but I didn't say that. I didn't step up for my son and for other people with Down syndrome. And that was devastating to me in that moment. So I just wanted to right that publicly for myself," he explains.
The video has garnered more than 870,000 views and an incredible outpouring of support including thousands of comments, many from other parents of kids with Down syndrome.
"Just found out my little baby girl has downs so thank u so much for this video!" wrote one commenter. "It really helps me see her as the kind sweet loving beautiful little girl I know she's going to be!"
Scott told CBC News that he has been blown away by the response to the video.
"It's just blown me away. It's certainly made up for it. To think that I missed that opportunity with those two kids, but now what it's doing? There's something karmic about that."
He added that he wasn't intending to judge the father who inspired his video because he also knew very little about Down syndrome until his own son was diagnosed.
And everyone do the Wop!!! Or whatever the heck dance my son is doing. pic.twitter.com/q0zzmH8K7O— Robb Scott (@RobbScottArt) February 19, 2016
"When they said, 'Your son has Down syndrome,' it was terrifying to me, because I had no idea," he told the news station. "But the information they give you is all bad, it's all scary. 'Here are the things that can go wrong.' Nobody comes in and says, 'Hold on – congratulations! This is a spectacular thing. Here's what you're going to learn, here's what you're going to do.'"
Scott said in spite of the grim predictions he was given, his son has taught him a great deal.
"If lessons of love and caring and acceptance and honesty are important to you, there is no better teacher," he said. "He has taught me so much."
"I don't know anyone he's been around who doesn't want to hug him and squeeze him and love him," he continued. "He just makes you feel happy and feel good about yourself. That's his gift."