Story highlights Trump walked away from the podium and flipped his belt buckle up and down to ridicule a key event in Carson's life

Trump also told the crowd in Fort Dodge that he could not possibly understand why anyone supports Carson

Washington (CNN) Donald Trump on Thursday told Iowa's voters that those who support Ben Carson are "stupid" to believe the "crap" that is his life story, part of a stunning 95-minute tirade that included his most aggressive attack yet on his closest competitor.

The real estate mogul's pugnacious demeanor was a stark departure from the far more restrained Trump on display at Tuesday's debate, when he declined to attack Carson while standing right next to him. He criticized the retired neurosurgeon repeatedly, said Hillary Clinton is playing the "women's card big league," ridiculed Marco Rubio as "weak like a baby" and vowed to "bomb the s*** out of (ISIS)."

Toward the end of his wide-ranging complaints about the country and competition, Trump mocked Carson's narrative about his violent temper as a youth that was calmed only when he prayed to God and asked for deliverance, an event that Carson describes as a miracle. That story of redemption has underpinned much of Carson's support in the Hawkeye State.

At one point, Trump walked away from the podium and flipped his belt buckle up and down to ridicule what Carson has described as a key event in his life: that Carson, as a boy, once tried but failed to stab someone only to have the knife broken by a belt buckle.

"So I have a belt: Somebody hits me with a belt, it's going in because the belt moves this way. It moves this way, it moves that way," Trump told the crowd, which laughed in response. "He hit the belt buckle. Anybody have a knife? Want to try it on me? Believe me, it ain't gonna work. You're going to be successful, but he took the knife and went like this and he plunged it into the belt and, amazing, the belt stayed totally flat and the knife broke."

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