Kelley Mack has died at the age of 33

Her sister posted on Kelley's Instagram account: "It is with indelible sadness that we are announcing the passing of our dear Kelley. Such a bright, fervent light has transitioned to the beyond, where we all eventually must go.

"Kelley passed peacefully on Saturday evening with her loving mother Kristen and steadfast aunt Karen present. Kelley has already come to many of her loved ones in the form of various butterflies [butterfly and heart emojis]. She will be missed by so many to depths that words cannot express.

"Kelley's Caringbridge link in her bio includes the 2-page formal announcement with information on her upcoming life celebration in Ohio on August 16th. 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****** proud of her."

Kelley was best known for her role as Addy in season 9 of The Walking Dead and some of her former colleagues paid tribute to her in the comments of the post.

Director Michael E. Satrazemis wrote: "I was lucky enough to create with Kelley on TWD. A bright light on every level. All my love to those who love her."

Actor Anthony Michael Lopez commented: "My deepest condolences, Kelley was such a sweet and happy soul and I'm happy to have met her. She fought so hard. Sending her and your family lots of light and love. Rest easy Kelley."

And actress Alanna Masterson posted: "What an incredible human. So proud to have fought alongside her in our final episode together."

Kelley also appeared in Chicago Med and 9-1-1, and was the voice match for Hailee Steinfeld's character, Gwen Stacy, in Spider-Man: Into the Spider-Verse.

The actress - who also starred in a number of commercials - will make her final appearance in Universal movie Ricky, which has yet to be released.

She is survived by her parents Kristen and Lindsay Klebenow, younger siblings Kathryn and Parker, grandparents Lois and Larry, and her "dearest boyfriend," Logan.