JPMorgan Vice Chairman Jimmy Lee dies

Jimmy Lee's "force of personality" and relentlessness made him an executive who always got deals done, former General Electric chief Jack Welch said Thursday, a day after the unexpected death of the 62-year-old JPMorgan vice chairman.

"It is with deep sorrow and a heavy heart that I inform you that our beloved friend and colleague, Jimmy Lee, unexpectedly passed away this morning," JPMorgan Chairman and CEO Jamie Dimon said in a statement. "Jimmy was a great friend, leader and mentor to me and so many others."

James B. Lee Jr. led the company's investment banking arm, and was known for his work on the syndicated loan market among other things.

He oversaw major mergers and acquisitions deals including the sale of General Electric assets, the General Motors and Alibaba IPOs (the two largest U.S. IPOs ever), the United-Continental merger and the Comcast-NBCUniversal merger, according to a company spokesman.

Read More On the Record: Jimmy Lee, JPMorgan Chase

"As Vice Chairman of our company and former head of our Investment Bank, Jimmy made an indelible and invaluable contribution to our company, our people, our clients and our industry over his nearly 40 years of dedicated and selfless service. Jimmy was a master of his craft, but he was so much more—he was an incomparable force of nature," Dimon said in his statement.

Lee told CNBC in 2010 he felt lucky for having his job.

"I love coming to work every day. I'm lucky in the sense that I get to work on, and many times run, our biggest transactions. I like the content of what I do and who I do it with," he said at the time.

Lee was exercising at his home in Connecticut when he felt short of breath, CNBC learned.

He is survived by his wife, Beth, and three children—Lexi, Jamie and Izzy—according to Dimon's statement.

"I've got a great wife, I got three great kids. I love being with them. To me the family unit is an important sacred place and I enjoy that the most," he told CNBC in 2010.

On CNBC's "Squawk Box," Welch said Thursday he had taken more than a dozen calls since Lee's passing from people who simply wanted to talk about his life.

"Everybody thought he was their best friend," Welch said. "People trusted him. He had an integrity that was built from years of always doing the right thing. He was a tremendous human being."

Hedge fund titan Dan Loeb shared a few thoughts on Lee's passing:

Jimmy loved Wall Street more than anyone I've ever known. He wasn't driven by money or deals but by his passion for people. There was no more loyal friend to be had on Wall Street, nor anyone whose wise counsel I valued more.

For example, when I told Jimmy I planned to send a Japanese CEO a letter announcing we were becoming active in its stock, he advised me to deliver it in person, which I did. When that act earned us praise in Japan for showing special sensitivity to the country's cultural customs, I repaid him by making him a tee shirt that said, "I advised Dan Loeb on his investment in Sony and all I got was this lousy tee shirt." Later, after Third Point became the first shareholder to meet with Fanuc in 40 years, Jimmy purchased a linen jacket in the company's distinctive corporate color—bright yellow—for me.

My last correspondence with Jimmy was a note from him titled "Bragging," where he told me about his son's admission into a highly competitive securities analysis program at Columbia Business School. He signed off by telling me that despite his long and successful career, his "greatest accomplishment" was his children. With Jimmy's passing, our community lost a little bit of its humanity and I lost the closest thing I've had to a big brother. My thoughts and prayers are with his family, who we discussed frequently, and who he was devoted to and loved so much.

—CNBC's Tom DiChristopher, Kayla Tausche and Scott Wapner and Reuters contributed to this report.

Disclosure: Comcast is the owner of NBCUniversal, the parent company of CNBC and CNBC.com.