One of Warren Buffett’s inner circle is leaving Berkshire Hathaway to start her own firm, according to a recent article in The Wall Street Journal.

Tracy Britt Cool, who the article describes as one of Buffett’s “key lieutenants in recent years,” joined Berkshire in 2009 at the age of 25 as his financial assistant, a role he reportedly created for her. In 2014, the article notes, she became chief executive of Berkshire-owned company Pampered Chef.

The article quotes Ms. Britt Cool: “I want to build a long-term platform and a long-term vehicle to acquire and build businesses. There are companies that I think there’s a lot of value in helping them get to the next level, but they’re too small for Berkshire.”

Ms. Britt Cool grew up in Kansas and attended Harvard Business School, where she co-founded a student group for women investors that traveled to Omaha—where she first met Buffett. She worked for him during the summer of 2009, and later that year Buffett hired her full-time.

During her decade-long tenure at Berkshire, Ms. Britt Cool focused on helping those companies in the portfolio that were facing struggles, the article reports, at various times serving as chairman of Benjamin Moore, Larson-Juhl, Johns Manville and Oriental Trading Co. In an interview, Buffett said, “She was the fireman. Anything I’ve assigned her she’s done a first-class job on.”