Tyrone Fahner, a former Illinois attorney general and leader of the prestigious law firm Mayer Brown as well as the Commercial Club of Chicago, died Monday at his Northfield home. He was 81.Mr. Fahner’s career spanned several decades in the public and private sectors, notably leading a task force investigating the 1982 Tylenol murders and serving as a mentor to young lawyers at Mayer Brown. He was a suburban Republican, but one of the young lawyers he took under his wing was Lori Lightfoot, a Democrat who went on to become a friend, a federal prosecutor and mayor of Chicago.“For me, Ty was a kind and generous friend who was a significant support to me at every stage of my career,” Lightfoot said in a statement. “He helped me understand how to be a good lawyer and professional. I became an [assistant U.S. attorney] because of his support and encouragement.” Mr. Fahner was born Nov. 18, 1942, in Detroit to Warren Fahner, an autoworker, and Alma Fahner, a telephone operator. He received a bachelor’s degree from the University of Michigan in 1965, then he returned to Detroit and earned a law degree from Wayne State University Law School in 1968. Mr. Fahner also earned a master’s degree in law from the Northwestern University School of Law. Tyrone Fahner studied under Jim Thompson at Northwestern University law school. Mr. Fahner later became an assistant U.S. attorney under Thompson. When Thompson was elected governor in 1976, he appointed Mr. Fahner to lead the state police.Mayer Brown/Provided While at Northwestern, Mr. Fahner became a protégé of Jim Thompson, who taught there.Mr. Fahner followed Thompson to the U.S. attorney’s office for the Northern District of Illinois, becoming an assistant U.S. attorney in the early 1970s under Thompson.Thompson became governor in 1977 and named Mr. Fahner to be the director of the state Department of Law Enforcement.In 1980, Thompson selected Mr. Fahner to serve as attorney general after the incumbent, William Scott, was convicted on tax evasion charges.During his tenure, Mr. Fahner was a member of the state task force investigating the 1982 Tylenol murders, in which seven people were killed in the Chicago area after ingesting cyanide-laced Tylenol. Tyrone Fahner in his office in 1982.Chicago Sun Times archives The case, which remains unsolved, created a nationwide panic and transformed the way over-the-counter medicine is packaged. The lone suspect, James Lewis, died last year and was never charged with the actual murders.Mr. Fahner lost his re-election bid for attorney general in 1982 and returned to private practice.“Ty was a dear friend and one of the most admired attorneys in Illinois recent history,” said former Illinois U.S. Attorney Dan K. Webb.Mr. Fahner joined Mayer Brown, serving on the firm’s management committee from 1985 to 2007, including as co-chairman from 1998 to 2001 and chairman from 2001 to 2007.“Ty led the firm through a time of incredible growth and change,” Mayer Brown said in a statement, noting his leadership through the firm’s three mergers with other law firms between 1998 and 2002.“In recent years, Ty continued to be involved in the Chicago community through his considerable civic and charitable work and, most recently, served as a key adviser to our former partner, Lori Lightfoot,” during her tenure as mayor, the law firm said in its statement. Tyrone and Anne Fahner in 2010. Jim Schulz/Chicago Zoological Society (Provided) “ Lightfoot’s mayoral opponents criticized her for having the support of Republicans such as Mr. Fahner.“Despite our superficial differences, we shared a deep bond as two working-class kids trying to make our mark in the world, and I am forever grateful that when I was so young, Ty saw something in me and a lifelong bond was forged,” Lightfoot said.Illinois Senate President Don Harmon, also a Democrat, was mentored by Mr. Fahner when starting his law career at Mayer Brown.“He believed in public service and encouraged people, including myself, to pursue it regardless of party,” Harmon said in a statement. “Even when you disagreed with him, and over the years I often did, you knew he was intellectually honest and his heart was in the right place.”Mr. Fahner was president of the Commercial Club of Chicago from 2010 to 2017, a not-for-profit group of senior executives from the area’s largest employers.Under Mr. Fahner’s leadership, the Commercial Club of Chicago aimed to raise awareness about the state government’s crushing pension debt, supported charter schools, advocated for expansion of O’Hare Airport and led an initiative on police accountability.Mr. Fahner also was appointed by President Ronald Reagan to serve on the Board of Foreign Scholarships from 1988 to 1991, and he served on the Commission for the Preservation of America’s Heritage Abroad, appointed by President George W. Bush, from 2007 to 2023.In 2012, Mr. Fahner became chairman of the Shedd Aquarium board of trustees after serving eight years on the board.Survivors of Mr. Fahner include his wife, Anne.Contributing: Michael Sneed