Imagine an ill-tempered six-year-old boy armed with nuclear weapons.

That's how Donald Trump would look like in case he succeeds in winning the White House, according to Michael D'Antonio, the author of the new book "Never Enough: Donald Trump and the Pursuit of Success" (St. Martin's Press). Writing for CNN, D'Antonio said he interviewed Trump extensively in 2014 and wrote his biography, starting from the time when the now Republican presidential front-runner was just a grade schooler.

"When I asked Donald Trump in 2014 about his temperament, he readily volunteered this: 'When I look at myself in the first grade and I look at myself now, I'm basically the same. The temperament is not that different,'" D'Antonio recalled.

In Trump's own book "The Art of the Deal," the man leading the Republican presidential race admitted that he gave his teacher a black eye because "the man didn't know what he was talking about."

D'Antonio said Trump confided to him that as a boy he just "loved to fight." Pressed to explain, he added, "Any kind of fight, I loved it, including physical."

He said Trump also told him that he doesn't respect the people he meets in life because "most people aren't worthy of respect."

In the first school he attended at the private Kew-Forest School in Queens, New York, the young Donald distinguished for being "a prep-school terror that no one could manage," D'Antonio said.

The author said this was the same temperament displayed by Trump during the GOP presidential debate in Detroit last Thursday. "Again in a coat and tie, Donald was the misbehaving bully boy. You could almost hear the squeals of little kids as Trump taunted his opponent, a United States senator, by repeatedly calling him 'little Marco' and boasted about the size of his own [manhood]. For Sen. Ted Cruz he used the phrase, 'Lyin' Ted.' The moderators, playing the role of teachers on the playground, struggled for control. 'Mr. Trump it's not your turn," said Chris Wallace, in a stern tone young Donald must have heard a thousand times," D'Antonio said.

Aside from his inability to control his temper, Trump has also shown "a child's inability to accept responsibility."

During the demolition of the building that occupied the Trump Tower site, D'Antonio recalled that Trump was caught destroying precious artwork that was supposed to be preserved. "He offered excuses of the sort you'd hear from a kid who just broke a window with a baseball," he said.

Trump has figured in many disputes, controversies and business failures where he "offered excuses but not a sense of responsibility," the author said.

"As he told me, Trump always operates with the assumption that human beings are vicious creatures. 'Man is the most vicious of all animals,' he has said. This is the assumption he has brought to the campaign," D'Antonio said.