Castle star Stana Katic posted a heartfelt message to fans after the ABC drama was canceled, after eight seasons.

"Your devotion to our show has carried us for these unforgettable 8 seasons," wrote Katic, who would not have been a part of any potential ninth season. "I'm lucky to have met and worked with and for the lot of you. I will always be grateful. BIG HUG."

ABC announced they were not renewing Castle Thursday night, which means Monday's season finale will double as a series finale. Castle's showrunners had prepared for this decision by creating an alternate ending for the episode that will give a sense of closure, as opposed to leaving fans with a cliffhanger.

Stana Katic and Nathan Fillion,<em> Castle</em>Stana Katic and Nathan Fillion, Castle

Castle finale promo: will Beckett die?!

Castleco-stars Molly Quinn (Alexis), Seamus Dever (Ryan), Jon Huertas (Esposito) and Toks Olagundoye (Hayley) shared their own reactions to Castle's cancellation on Instagram and Twitter.

Castle's series finale airs Monday at 10/9c on ABC.