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Story highlights

Ben Carson reveals he wasn't always soft-spoken

Comments come after Donald Trump criticized his low energy level

(CNN) —  

Ben Carson says he’s soft-spoken now – but he hasn’t always been so calm.

“As a teenager, I would go after people with rocks, and bricks, and baseball bats, and hammers. And, of course, many people know the story when I was 14 and I tried to stab someone,” Carson said Sunday on NBC’s “Meet the Press.”

“You know, fortunately, you know, my life has been changed,” he added. “And I’m a very different person now.”

Carson’s comments came after Donald Trump, his leading opponent for the Republican presidential nomination, said at a rally in Miami on Friday that Carson has even less energy than Jeb Bush, who the developer has repeatedly called a “low-energy” candidate.

“Ben Carson is super low energy, right? He’s super low,” Trump said. “Super low energy. We need tremendous energy. We need tremendous energy.”

Carson told NBC’s Chuck Todd that he thinks people mistake his soft-spoken manner with a lack of energy.

“I do have a tendency to be relaxed,” he said. “I wasn’t always like that. There was a time when I was, you know, very volatile. But, you know, I changed.”

That’s when Carson mentioned his violent childhood growing up in Detroit, Michigan. He’d also detailed his youth in his book “Gifted Hands,” writing about nearly stabbing a friend during an argument before beginning to read the Book of Proverbs and applying its lessons.

RELATED: Carson: ‘My energy levels are perfectly fine’

Trump and Carson are also exchanging shots over religion after Trump told a crowd in Iowa of Carson’s faith: “I mean, Seventh-day Adventist, I don’t know about. I just don’t know about.”

In a separate interview on “Fox News Sunday,” Carson noted that Trump “went ballistic” when Carson has questioned whether Trump is – as he says – Presbyterian. Carson later apologized.

But Trump said Sunday on ABC’s “This Week” that he has nothing to apologize for.

“I know nothing about it really. I’m a Presbyterian and I had mentioned that, and I did say I don’t know about it. And in fact those are my exact words,” Trump said. “I didn’t say anything bad about it. I just don’t know about it. I would certainly give an apology if I said something bad about it. But I didn’t. All I said was I don’t know about it.”

Carson, a retired brain surgeon, pushed back against Trump on the “low energy” attacks in Iowa on Saturday.

“As I’ve said many times, there have been many times where I’ve operated 12, 15, 20 hours, and that requires a lot of energy,” Carson said. “Doesn’t require a lot of jumping up and down and screaming, but it does require a lot of concentration.”

Trump has taken aim at Carson after two polls showed that Carson had surpassed him as the Republican front-runner in Iowa.

“Donald Trump falls to second place behind Ben Carson,” Trump said, pretending to read a headline. “We informed Ben, but he was sleeping.”

Then, at a rally in Jacksonville on Saturday, Trump expressed incredulity at Carson’s rise.

“I don’t know what the hell is going on there,” he said. “I don’t get it!”

Correction: An earlier version of this story had misstated the show on which Carson appeared. He spoke on NBC’s “Meet the Press.”

CNN’s Eugene Scott contributed to this report.