In last night's (February 12) midseason premiere 'Nebraska', Rick (Andrew Lincoln) was forced to shoot threatening newcomers Dave (Michael Raymond James) and Tony (Aaron Munoz).
"I think this was a particularly good episode coming back because the two guys in the bar represent new threats," Kirkman told Entertainment Weekly. "And they are really just the tip of the iceberg."
He added: "It's really good to come back and be off of the farm and see that there are more dangerous things out there than the zombies. Things just keep getting worse from here."
Last month, Walking Dead showrunner Glen Mazzara claimed that the latter half of the show's second season "accelerates the storytelling".
"I think if the whole season had run concurrently week-after-week, you would have been able to see that the slow episodes actually build up pay-off for the fast episodes," explained Kirkman.
"But, as it stands right now because of the break, it's like, slow episodes in the fall and fast episodes in the spring."
The writer also confirmed that pre-production continues on the 16-part third season of The Walking Dead, which was confirmed in October.
"Right now we're finishing up our third week of writing," he said. "We're constantly shocking ourselves. I can say right now the third season is going to be insane."
The Walking Dead continues on Sundays at 9/8c on AMC. The show resumes on FX in the UK on February 17.
> Andrew Lincoln interview: 'Walking Dead is the coolest job in town'
Watch a promo for The Walking Dead below: