9-1-1 and The Walking Dead actress Kelley Mack has died at the age of 33. "It is with indelible sadness that we are announcing the passing of our dear Kelley," Mack's sister Kathryn announced via the Chicago Med alum's Instagram page on Tuesday, August 5. "Such a bright, fervent light has transitioned to the beyond, where we all eventually must go." The post shared that Mack "passed peacefully" on Saturday, August 2. Her mother Kristen and aunt Karen were present at the time of her death.