The industry is mourning the passing of David Tittsworth, the former longtime president and CEO of the Investment Adviser Association in Washington.

A Capitol Hill veteran, Tittsworth died Wednesday morning after a long battle with multiple myeloma. He was 66.

“David will be remembered as a passionate, dedicated, articulate and effective advocate for the investment advisory community and for the importance of fiduciary advice,” said Karen Barr, IAA’s president and CEO, in a note to IAA members. “Over the nearly two decades I worked with him, David became not just my colleague and mentor, but a valued and cherished friend.”

After leaving IAA’s helm after 18 years, Tittsworth became counsel in Ropes & Gray’s investment management practice in Washington. Before his long tenure with the IAA, Tittsworth worked in various positions on Capitol Hill, including as counsel to the House Energy & Commerce Committee chaired by Rep. John Dingell.

Tittsworth joined IAA when it was known as the Investment Counsel Association of America; at the time the organization had two employees, was headquartered in New York, and served 200 member firms that collectively managed $1 trillion in assets.

An accomplished pianist and avid cyclist, Tittsworth moved the operation to Washington and, over the next 18 years, “developed it into a trade association widely respected among regulators, legislators and its organizational peers,” Barr said.

When Tittsworth retired from IAA in March 2014, IAA had more than 500 member firms managing more than $12 trillion. “Building on his foundation, the IAA now serves over 650 member firms managing more than $25 trillion,” Barr said.

Industry officials expressed their condolences on social media. Skip Schweiss, president of TD Ameritrade Trust Co., and managing director of advisor advocacy and industry affairs for TD Ameritrade Institutional, tweeted: “Oh, what terrible news: the passing of David Tittsworth. What a superb guy.”

Barbara Roper, director of investor protection for the Consumer Federation of America, added in a separate tweet: “David was one of the best, most decent human beings I’ve ever had the good fortune to work with. This is terrible news indeed.”

A go-to source on all things advisory related, Tittsworth was an eager and gracious source to the media. His lengthy emails were chock-full of information, and always ended with an open invitation: “All the best. Happy to discuss.”