"Game of Thrones'" writer-producers say the shocking deaths on Sunday's episode were intended to remind viewers no characters are safe..

Robb Stark and his mother Catelyn, lead characters who have been on the gritty medieval series since it began three seasons ago, were ambushed and slaughtered in what fans of the books that inspired the show refer to as the iconic Red Wedding scene. Also killed in the massacre were Robb's pregnant wife and all of his men.

The development means the departures of prominent cast members Richard Madden, Michelle Fairley and Oona Chaplin.

Asked how shooting the scene went, co-showrunner David Benioff told EW.com: "It's weird to say, 'Oh, it went great.' Because we're not just killing characters. We're losing these actors who have been with us since the beginning. It's hard because you love the actors. But it goes back to that first season, that some of the people we loved the most, whether Jason Momoa or Sean Bean [played characters that were killed off.]"

"It's the kind of thing that hammers home that everybody's life is precious and precarious," co-showrunner Dan Weiss said. "When you can't take for granted that a character you love on the show is going to be around forever, it makes you pay more attention to them."