Kamen says he watched as the man tried to navigate his way out of the parking lot and into the mall but hit a brick wall when he tried to find a way over the curb.
"I'm thinking, 'So we've got the technology to put guys on the moon, under the oceans ... but a full-grown adult, a pretty healthy-looking guy sitting in a wheelchair, can't get into a mall?'" he asked.
After seeing the same man a few times around the mall, Kamen realized something: The loss of mobility was one thing, but the loss of dignity was far more severe.
While picking up his nightly dinner -- "a coffee ice-cream cone" -- in the mall's food court, Kamen saw the man at a food counter struggling to be seen by the clerks on the other side.
At virtually every store, Kamen saw that the man was looking up at things he couldn't reach and that the world seemed almost inaccessible.
"If a human being was a sack of potatoes, you could throw 'em in a wheelbarrow and move 'em around," he said. "But a human being is not a sack of potatoes and mobility is not the only thing you lose when you lose is the human capability to stand up.
"You lose the ability to look your peers or your spouse in the eye. You lose the ability to interact with people over a counter or to take something off a shelf or get into a mall. Every curb and every flight of stairs might as well be the bars on the door of a jail, and I just said, 'This can't be right.'"
So Kamen started thinking about what makes human mobility, communication and lifestyle possible: balance.
"It's a very difficult skill," he said. "Ask your mother -- as a baby, there are probably only two things she remembers: your first steps and your first words. Because being able to stand up and balance and get around is a big deal."
With that in mind, Kamen got to work on what would become one of his proudest endeavors -- the Independence Ibot Mobility System, a wheelchair that can climb stairs and traverse uneven terrain, and uses a self-balancing system that can prop the chair up on two wheels, allowing the user a chance to see the world at eye level.
Instead of trying to just build another wheelchair, Kamen wanted to give back what he believes is really lost when someone loses the ability to walk.
"It took a lot of years to learn how to balance -- I mean, there's a reason kids take a long time to learn how to stand up and get around," he said. "But we did it, and we built the Ibot and virtually every disabled person I've ever seen get into it gets emotional about being able to stand up. It's a really big deal."
The work done on the Ibot led to the Segway scooter, which uses similar technology to balance a rider on two wheels.
When Dean Kamen was growing up, he had little taste for school.
As a high school student, he found himself not looking for the right answers but instead, looking for the answers he thought the teachers liked best.
That turned him off to school and -- assuming work was more of the same -- kept him from working for anyone but himself.
Although Kamen attended Worcester Polytechnic Institute, he didn't graduate. Instead, he used his access to the academic community to get his business off the ground.