Donald Trump speaks during a campaign event at Iowa Central Community College in Fort Dodge, Iowa, on Thursday. REUTERS/Scott Morgan

FORT DODGE, Iowa -- For an hour and 35 minutes, Republican front-runner Donald Trump vented about everything that's wrong with this country and this election.He said he would "bomb the s---" out of areas controlled by the Islamic State that are rich with oil and claimed to know more about the terrorist group than U.S. military generals. He ranted about how everyone else is wrong on illegal immigration and how even the "geniuses at Harvard" have now backed his way of thinking. He accused Hillary Rodham Clinton of playing the "woman's card," and said Marco Rubio is "weak like a baby." He signed a book for an audience member and then threw it off the stage. He forgot to take questions like he promised. And he spent more than 10 minutes angrily attacking his chief rival, Ben Carson, at one point calling him "pathological, damaged."Gone was the candidate's recent bout of composure and control on the campaign trail. As Trump ranted on and on, campaign staffers with microphones who were supposed to take questions from the audience instead took a seat, trying to cheer their boss here and there. The audience laughed at times and clapped for many of Trump's sharp insults. But an hour and 20 minutes into the speech, people who were standing on risers on the stage behind Trump sat down. The applause came less often and less loud. As Trump skewered Carson in deeply personal language, a sense of discomfort settled on the crowd of roughly 1,500. Several people shook their heads or whispered to their neighbors.Carson wrote in his autobiography that as a young man he had a "pathological temper" that caused him to violently attack others -- going after his mother with a hammer and trying to stab a friend, only to have the blade stopped and broken by the friend's belt buckle. In recent days, those accounts have come under scrutiny, and Carson has had to clarify or correct some of the details.Trump said he doesn't believe Carson is telling the truth and questioned how a belt buckle could stop a blade. He stepped away from the podium and acted out how he imagined such an attack would happen, with his own belt buckle flopping around. He asked if anyone in the audience had a knife to try out his theory. His Secret Service agents, who just joined his detail this week, stood guard."Carson is an enigma to me," Trump said. "He said that he's 'pathological' and that he's got, basically, pathological disease... I don't want a person that's got pathological disease."Trump repeatedly said he doesn't believe there's any cure for such a disease, and he said he doesn't believe that Carson was truly changed by divine intervention, as he writes in his book."If you're a child molester -- a sick puppy -- a child molester, there's no cure for that," Trump said. "If you're a child molester, there's no cure. They can't stop you. Pathological? There's no cure."And yet Carson is doing well in the polls, Trump said in disbelief."How stupid are the people of Iowa?" Trump said. "How stupid are the people of the country to believe this crap?"Trump started the speech looking exhausted, his voice hoarse. This was his fourth state in four days. A sense of anger built as Trump listed off everything wrong with the country and everything wrong with his rivals. His voice got louder and stronger, his hands gripping the podium. He would be a unifier, he said, a winner. Then he wondered aloud if he should just move to Iowa and buy a farm."I've really enjoyed being with you," Trump said as he drew to a sudden but long awaited end. "It's sad in many ways because we're talking about so many negative topics, but in certain ways it's beautiful. It's beautiful."