Kim Jong Un was 'stressed,' 'angry' as a child, former family bodyguard says "His personality was explosive," the former bodyguard said.

 -- An ex-bodyguard for North Korea’s former dictator Kim Jong Il said the country’s current leader, Kim Jong Un, lived an isolated childhood that left him “stressed” and “quick-tempered.”

Lee Young-guk, who was one of the Kim Jong Il's personal bodyguards for 11 years, told ABC News' Bob Woodruff that the man who has drawn worldwide censure for rapidly advancing his country’s nuclear weapons program lashed out as a young man.

“He was stressed and had no one to play with his own age,” Lee said in an interview in Toronto last October. “There were only adults, who educated and played with him.”

Watch the full story on ABC News "20/20" this Friday, Jan. 12 at 10 p.m. ET.

Kim Jong Un, believed to be 35 years old, has in recent months engaged in a war of words with President Donald J. Trump amid high tensions on the Korean Peninsula. Lee painted a picture of a combustive young man.

“His personality was explosive,” Lee said. “When he was angry, he acted without considering the consequences.”

Lee observed Kim Jong Un and Kim’s half-brother, Kim Jong Nam, when he was assigned to protect their father, Kim Jong Il, who led North Korea from 1994 until his death in 2011.

While his half-brother, Kim Jong Nam, was treated much better by their father -- who originally groomed him as a successor -- Kim Jong Un’s existence was largely kept secret, according to Lee.

That isolation left its mark, according to the bodyguard.

“He was quick-tempered,” Lee said. “He doesn’t care about what others think. He doesn’t feel sorry for other people. He does whatever he wants. He would yell at the ladies. He was like that.”

Lee said he saw Kim Jong Un “many times” when the boy was 6 or 7 years old. “When playing with a dog in the garden, Kim Jong Un’s personality was quick-tempered not calm,” he said.

The future North Korean leader “would run around in the grass and flower garden, fall over smashing things,” Lee added.

The competition to become a bodyguard for North Korea’s leader was fierce, Lee said. His character, personality, stamina and morals were measured against those of 14,000 others candidates, he said.

“You have to be good at shooting guns,” Lee said. “Then Taekwondo, things like throwing knives, swimming, and marching, these are the first. And the second is serving Kim Jong Il with loyalty, that’s also the third and the fourth.”

Lee eventually tried to escape North Korea but, he said, he was caught and kidnapped in China and was returned to the North. He said he was sent to a labor camp in 1995 and was tortured there. His captors whipped his legs and knocked out his teeth, he said.

Then, in 2002, he finally made it out by again escaping across the border into China. He is now applying for asylum in Canada.