(WKBN) – Kelley Mack, an actress who appeared on shows including “The Walking Dead,” “9-1-1,” and “Chicago Med” has died, according to a message posted to her official Instagram account.

Mack died Saturday, according to her sister. She was 33.

“It is with indelible sadness that we are announcing the passing of our dear Kelley,” reads the post, which included a photograph of Mack. “Such a bright, fervent light has transitioned to the beyond, where we all eventually must go.”

Mack had suffered from glioma, a tumor that affected her central nervous system, according to a two-page announcement of her passing shared by family. There are several types of gliomas, according to the Cleveland Clinic; all types they are malignant, and usually grow in the brain or spinal cord.

Kelley and her family had also been documenting her treatments, which included surgery and proton radiation therapy. (Gliomas usually require a “combination of treatments,” according to the Cleveland Clinic.)

Mack, whose IMDb resume goes back to 2008, had appeared in a number of shorts, feature films and television series, but was perhaps best known for her role as Addy in “The Walking Dead.” She also appeared on “Chicago Med” and “9-1-1.”

Co-stars of Mack’s shared their memories of working with the actress on social media.

“What an incredible human,” Alanna Masterson, of “The Walking Dead,” wrote of Mack. “So proud to have fought alongside her in our final episode together.”

“I feel so blessed to have crossed paths with you Kelley,” said “Walking Dead” alum Gustavo Gomez. “You were such a bright light. Rest peacefully, friend.”

Mack’s family has announced that a celebration of life will be held on August 16 in Glendale, Ohio. Another celebration will be planned for Los Angeles at a later date, they said.

“She will be deeply missed but forever remembered for her talent, kindness and vibrant spirit,” they wrote.