Valeant has been under significant pressure from lawmakers and shareholders after the company hiked prices for certain drugs. On Sunday, The Wall Street Journal reported that Pearson was key in making those decisions. Valeant's board ousted Pearson in March. Last week, Valeant named Joseph Papa to succeed Pearson.
Valeant declined CNBC's request for comment. CNBC could not immediately locate Pearson for comment.
"I would've been amazed if it hadn't come from the top. Pearson … he certainly seemed like the sort of person who forged all important policies on the company," Buffett said. "It was an important policy to jack up prices dramatically, unbelievably almost, for certain drugs that people really don't have a substitute for."
"We had at Berkshire over the previous years … at least two large holders who were urging us to buy, and part of the pitch was what they could do with the pricing."