Casey LaLonde, a grandson of Joan Crawford who helped preserve her legacy as a Hollywood legend through public screenings of her films and home movies, has died. He was 54.

LaLonde died suddenly Monday at his home in Downingtown, Pennsylvania, his family announced.

Just last month, LaLonde was on hand at the TCM Classic Film Festival to help introduce a 4K restoration screening of the Crawford-starring Letty Lynton (1932), a big hit back in the day. Because of legal issues, the Warner Bros. film had been pulled from theaters in 1936 and was not seen publicly in the ensuing 90 years.

“It would be an understatement to say this was one of my best days, ever,” he wrote of the TCM event in a post on a Joan Crawford Instagram account that he managed.

He was scheduled to attend another screening of the film in July at the American Legion’s Hollywood Post 43 theater.

LaLonde also made appearances in support of his Oscar-winning grandmother at the TCM Classic Cruise, the UCLA Film & Television Archive, the Hollywood Heritage Museum — he hosted an evening of newsreel footage and Crawford’s home movies there in October — the Museum of Modern Art and the Fox Theatre in Toronto, among other venues.

LaLonde’s mother, Cathy Crawford LaLonde, and her twin sister, Cindy, were adopted by the Mildred Pierce star and her fourth husband, Pepsi-Cola CEO Alfred Steele, in 1947, soon after their biological mother’s death.

The actress’ first two kids also were adopted, daughter Christina in 1939 (when Joan was divorced from her second husband, actor Franchot Tone) and son Christopher in 1943 (a year after Joan had married actor Phillip Terry.)

Christina alleged that Joan physically and emotionally abused her and Christopher in her best-selling 1978 memoir, Mommie Dearest, which was adapted for the 1981 film that starred Faye Dunaway. Cathy and Cindy, on the other hand, had positive things to say about their mom.

LaLonde’s family noted that “Casey was an amazing advocate for his grandmother’s legacy by taking control of the narrative that has been presented about Joan and focusing on her career and what she meant to him and his mother. … He loved meeting her fans and had built amazing friendships throughout this community.”

LaLonde was born on March 16, 1972, in Alexandria Bay, New York. He attended Northern Lehigh High School and Penn State University, then earned his master’s degree from Virginia Commonwealth University in 1999.

He spent years working for local government, including a stint as township manager in West Goshen, Pennsylvania, and was a consultant and management strategist at the civil engineering firm Herbert, Rowland & Grubic Inc., his family noted.

Survivors include his wife of more than 30 years, Heather; his sister, Carla; and nieces and nephews Olivia, Oscar, Ivan, Vivien, Theodore and Veronica. His mother died in 2020 at age 72, his grandmother in 1977 at age 73.

Donations in his memory can be made to the Downingtown Library and Tri State Bird Rescue and Research.