Republican presidential candidate Ben Carson. Joe Raedle/Getty Images After hosting a raucous press conference Friday evening to respond to several questionable claims about his past, Republican presidential hopeful Ben Carson may have more explaining to do.

The Wall Street Journal fact-checked another claim in the retired neurosurgeon's 1990 autobiography, "Gifted Hands," and found more evidence of a potentially fabricated story. The Journal's Reid Epstein reported:

"Mr. Carson writes of a Yale psychology professor who told Mr. Carson, then a junior, and the other students in the class—identified by Mr. Carson as Perceptions 301—that their final exam papers had “inadvertently burned,” requiring all 150 students to retake it. The new exam, Mr. Carson recalled in the book, was much tougher. All the students but Mr. Carson walked out.

The professor came toward me. With her was a photographer for the Yale Daily News who paused and snapped my picture,” Mr. Carson wrote. “‘A hoax,’ the teacher said. ‘We wanted to see who was the most honest student in the class.’” Mr. Carson wrote that the professor handed him a $10 bill."

However, The Journal spoke with Yale Librarian Claryn Spies, who said that there was never a class called Perceptions 301 at the school, and a search of YDN turned up no sign of such a picture.

It's another confounding instance of inaccuracies in anecdotes about the life and belief system of Carson.

Ben Carson. Joe Raedle/Getty Images A CNN story earlier in the week researched claims that Carson had made in his autobiography about having a violent streak as a teenager, attacking his mother with a hammer and attempting to stab a friend. Carson claimed that it was those instances in his past that caused him to find God and assume a calming temperament.

But CNN wasn't able to find anyone from Carson's past to corroborate his stories of past violence, and most remembered him as the same soft-spoken person he is today. Carson argued many of those stories happened as much as 50 years ago.

Politico also disputed a story in "Gifted Hands" — and one Carson has told repeatedly on the campaign trail — in which he said he turned down a scholarship offer from the US Military Academy at West Point. It turns out that Carson never applied to West Point.

During the press conference on Friday, Carson admitted that he had never received a scholarship offer from West Point. But he said he had received encouragement to attend after meeting with a top US Army general.

On Friday he hit back at the media for supposedly inventing controversy.

"There is a desperation on behalf of some to try to find a way to tarnish me because they have been looking through everything," Carson said. "They are getting desperate. So next week it'll be 'my kindergarten teacher who said I peed in my pants.' I mean, it's ridiculous!"