Actor Kelley Mack, best known for playing Addy on “The Walking Dead,” died over the weekend, her family announced.
She was 33.
“Such a bright, fervent light has transitioned to the beyond, where we all eventually must go,” her sister Kathryn wrote on Mack’s Instagram on Tuesday.
Mack, born Kelley Lynne Klebenow, passed away “peacefully” on Saturday evening, surrounded by her mother Kristen and aunt Karen after “battling glioma of the central nervous system,” the family said in a statement.
The star announced in January that she was diagnosed with diffuse midline glioma, an extremely rare type of astrocytoma cancer. Diffuse midline gliomas are central nervous system tumors, meaning they begin in the brain or spinal cord. It’s treated by surgery, radiation therapy, and chemotherapy, according to the National Cancer Institute.
In an Instagram post, Mack explained that late last year she felt “persistent lower back pain and thought I slipped a disc.” Weeks later, she experienced “neuropathic itching in my right quad” followed by “shooting pains in my legs and back,” that forced her to sleep in a recliner for a month because lying down “was too painful.”
Finally, on Thanksgiving Eve, she wrote that she had emergency MRIs done at a hospital, “which revealed an abnormal mass in my spinal cord.”
At the time, she was receiving radiation treatment in Cincinnati, where her family lives.
“I am very grateful to have such a supportive and loving family and boyfriend, who have been with me every second of this process. It has been a very emotional and challenging time, truly testing my mental fortitude, faith, and physical strength,” Mack wrote. “This experience has brought me closer to God, and I am leaning on him and trust his plan for me.”
In March, she shared a video on Instagram of herself walking up the stairs, writing: “I’ve been up and down these stairs now 2x in the past few days. It’s a big deal for me.”
Mack’s sister told her followers in the Tuesday post: “She would want you all to know how much she loves you.”
“And as her sister, I want you all to know how brave that tough SOB was, especially when she decided to make the leap to be reunited with God. I’m so f***ing proud of her,” she continued.
The Tuesday tribute post said Mack has already visited her loved ones “in the form of various butterflies.”
“She will be missed by so many to depths that words cannot express,” her sister wrote.
The family statement described Mack as a vibrant, creative person whose “love for storytelling blossomed at a young age, when she received a mini video camera as a birthday gift.”
She went on to act in commercials as a child, then on to the big screen. She also worked in commercial acting, voice-overs and producing.
Mack appeared in season 9 of “The Walking Dead” from 2018 to 2019 as Addy, as well as “Chicago Med” in 2022 and an episode of “9-1-1” in 2019, according to her IMDb profile. Recently, she appeared in the 2024 films “Mr. Manhattan” and “Delicate Arch.” She had been promoting the 2025 film “Universal on her Instagram in recent months.
“Kelley was known for her warmth, creativity, and unwavering support for those around her. She cherished time with her family and friends, finding joy in collaboration and storytelling. Her infectious enthusiasm and dedication to her work inspired countless others in the industry and beyond,” the statement said.
A celebration of life ceremony is scheduled in Ohio for Aug. 16.
Mack is survived by her mother and father, Kristen and Lindsay Klebenow; her sister, Kathryn; her brother, Parker; her grandmother and grandfather, Lois and Larry Klebenow; and her boyfriend, Logan Lanier.
