Asked by Good Day Sacramento if he was shocked by news of Lincoln's departure, Riggs answered, "Of course, yeah."
"I mean, Andy has been on the show for so long and he's had to leave his family every single year, so I was surprised, but at the same time, it's gonna be good for him to get back to his family and raise his kids," Riggs said of the English actor, who has headlined the series since its 2010 debut.
Riggs exited the series midway through season 8 when Carl was revealed to have received an incurable walker bite that ultimately forced the teenager to shoot himself.
Six months after Carl Grimes' death, Riggs told audiences at Walker Stalker Con Nashville he was "very surprised" when he learned Carl would be killed off.
"It was very surprising," Riggs said. "Not something me or anyone would have expected."
Riggs admitted in February then-showrunner Scott Gimple "didn't mention" Carl would be dying in a meeting with Riggs and his parents ahead of production on season 8.
"Usually he doesn't bring me in with my parents, usually," Riggs told Entertainment Tonight. "I had actually talked with him months before, just like to lay out the season and everything, but he didn't mention that."
Despite his unexpected severance with the show after nearly eight full seasons, Riggs said it "just kind of made sense" for Carl's death to happen "for the story and everyone else's story."
Unlike Riggs, Lincoln chose to leave The Walking Dead — and Carl's death may have played a part in Lincoln's choice to move on.
"I think that when we got the news that Carl was dying on the show — it certainly for me — it felt like very much a bookend of a much bigger journey that began in the hospital," Lincoln told ComicBook.com in April.
"Searching for his wife and his son were the two engines that kept this man alive at the beginning of the show eight years. To lose the second engine that fueled him, at this point, certainly did feel, to me personally, not just the end of a chapter but a book, really."
The Walking Dead returns with its ninth season this fall on AMC.