There's no denying that Rick Grimes, the protagonist of AMC's The Walking Dead, has taken a turn since he first rode a horse into Atlanta looking for his wife and son after waking up in the middle of a zombie apocalypse two seasons ago.

[Spoiler alert!]

In fact, he may just be moving from the "hero" to "anti-hero" category now that he's killed countless Walkers, blown away two dangerous human types in a bar, killed his best friend Shane, macheted a former inmate and hacked off Hershel's leg to keep him from turning into a Walker.

It's been one tough road for the former lawman and his small band of survivors as they hunt for safe haven and possibly find it in a prison after eight months on the run, and English actor Andrew Lincoln, who plays Rick, is thrilled to see the evolution, or maybe de-evolution, of his character.

"I think his humanity is pretty intact, but his ruthlessness or his decision-making has very much moved into a Shane point of view," said Lincoln during a conference call with journalists. "We obviously meet this gang at such a desperate and low act in their story, in [season three's first episode] that they're pushed into this position to take something that probably, in any other circumstances, would have been a death wish."

Even in these circumstances, taking on a prison filled with Walkers could still be considered a death wish. But in the story, Rick's wife Lori is pregnant, and they're surrounded by Walkers at every turn. So the unforgiving walls of a prison seem like a possible safe haven.

However, the living prisoners the group found wound up on the wrong side of Rick, and a couple of them paid the price, as Rick drove a machete through one's skull and chased another one into a prison yard filled with Walkers.

"There is an uncompromising nature that I think has happened over time to Rick. And also I think that the other thing to bear in mind is that he is the most isolated, I think, even within his group and in his relationship with everybody in the group, especially his wife," said Lincoln. "So I don't think he's the most stable. Certainly when I was playing it [and killing the inmates], I wanted it to be an instantaneous, almost Pavolvian reaction to this situation, which in season one and season two, certainly, I think, he wouldn't have been so quick to make that judgment call."

For Lincoln, "That's one of the beautiful things. That's one of the joys of playing Rick. ... The moral ambiguity in the show is the most interesting part for me, certainly as an actor, because in any other world, in any other situation that wasn't, you know, hell, you wouldn't make these judgment calls or you wouldn't be pushed into this corner to make these calls."

The thing that helps Rick justify his decision is that the group's safety is his priority, he said. "So it is a sort of selfless act even though it is incredibly brutal. ... It's born out of a selflessness," he said. As far as his humanity, "I think certainly as we go through this season it diminishes and diminishes, is all I will say."

Looking back through the first two seasons, Rick appeared to have little choice in his violent acts. He killed the guys in the bar because they would have killed him and endangered the group. He killed Shane because Shane was going to kill him. But the prisoners, while the first one threw a Walker on him and deserved that machete, the second one was just running away. Rick's calculated act of locking the man in with Walkers to almost certain death showed us a very changed man.

"I always say that with Rick, everything costs, every responsibility for each death costs him, and by definition changes him. Which is one of the great things about playing him, is that he's very mercurial. I mean, he keeps developing and moving, and it's kind of elusive," said Lincoln.

Killing the prisoners who he didn't know was one thing. But hacking off Hershel's leg in a horrifying moment also told us everything about Rick's season-three state of mind.

"It was an incredibly shocking moment, actually," said Lincoln. Shooting the scene "was the most intense, adrenaline-fueled thing that I probably had ever done in this show."

Lincoln didn't believe they were going to get away with showing the graphic scene on television. "Apparently because I'm saving his life or attempting to save his life, that's why we were allowed to show it, which really makes me laugh. I'm trying to save his life with a meat cleaver, which is probably the first time I've ever tried to save anyone's life with a meat cleaver. But certainly that was an incredibly distressing and strange out-of-body experience. But just rest assured there are countless others in this season. I think that it always seems to be the case that the writers' room are trying to up the ante each episode," he said.

"I kind of made the fatal error of walking into the writers' room and suggesting, 'What do you think Rick's breaking point is?' And certainly this season we find out," said Lincoln. "I think the thing I was constantly surprised at is—certainly over the last few seasons—is his incredible resilience and resolve and being able to just come back from these tumultuous, cataclysmic kind of events."

However, as the season progresses, not all the group will be on board with Rick's actions. "Over the course of this season I think that people start to doubt many things in Rick, but certainly his decision-making as a leader is very much called into question this season." Especially involving the "primal" moments that seem "borne out of fury and rage" even as he protects the group.

"I wanted to sow the seeds of doubt, certainly in the first two episodes, that there is some decision-making that is pretty irrational and some choices that he makes that, like in a classic Greek tragedy, come back to haunt him," said Lincoln. "He is sort of coming apart, but he's doing a very good impersonation of someone holding it together at the moment. ... Like you go down the rabbit hole for, you know, 30 seconds, and you go with him. And then suddenly everyone comes up for air and you went, 'What the hell just happened then?' And I wanted that to be the experience, certainly, that I was feeling as an actor, and hopefully that translates to this, to the viewer."