If you ran into Amazon founder and CEO Jeff Bezos in a Seattle coffee shop, it might take you a minute to realize who he is. The man who forever changed the way we shop comes off as an everyman, with a friendly personality and an easy laugh.
But those who have worked for him say he can also be a tough and intimidating boss who expects results and has no patience for anyone who doesn't measure up.
"He's very demanding, but I think most good leaders are," former Amazon.com executive John Rossman said. "He expects great results. He has a low tolerance for thinking small, acting small or not being extremely sharp."
Randy Miller, another Amazon former executive, agreed.
"If you start giving rationalizations or excuses, he'll just tear you to shreds," he said. He recalled a meeting with Bezos in which a presenter was not prepared and had a half-baked idea.
"I can remember at one point [Bezos] said, 'I don't know if this is—sheer stupidity or gross incompetence,'" he recalled. "I remember one person said to me, 'Oh my God. I was just praying that I was going to have a heart attack so this would stop.'"
Read MoreIs that online review site telling you the truth?
Bezos may be tough on his employees, but Amazon executives say it's always in service to the company and customers.
"He is harsh on the result, and on the problem, not on the individual," said Nadia Shouraboura, a former executive who was at one point a part of Bezos' inner circle. "He thinks of the result. That there is a disappointed customer, or there is a missed promise."
Miller thinks Bezos' tough management style pushes executives to grow.
Read More Is Amazon's new Fire phone scorching or all smoke?
"Those who survive that, do come back and do better," he said. "If you continue to provide the kind of the results that you're supposed to get, the things you're responsible for can grow quite rapidly."
—By CNBC's Michael Beyman
CNBC reports on the spectacular growth of the online giant Amazon. "Amazon Rising" premieres Sunday, June 29 at 9 p.m. ET/PT