Apparently the season three finale of The Walking Dead was originally even darker and more upsetting than the finale we actually got. This wasn't just the plan - this was actually shot. The decision to make the ending more "uplifting" came after season three showrunner Glen Mazzara decided to leave the show. It is unclear whether Mazzara or incoming showrunner Scott Gimple decided to change the ending.
Entertainment Weekly got the scoop directly from Milton's mouth: actor Dallas Roberts had this to say:
“Originally, the beating scene that started the episode wasn’t there. Originally, I showed up and was led into the room where Andrea was…and then [The Governor] shot me in the stomach, completely unexpectedly.… There was a lot more of Milton trying to open the door and him trying to free her from the chains. And then there was a section where he was going to wrap the chain around the neck and try to choke her to death before he turned so she wouldn’t have to deal with Walker Milton, or Biter Milton, as it were.…They both desperately wanted for that to work but at that point he had bled out so much. So he pulls and pulls and pulls but he doesn’t get it done and he falls against the wall and is passed out. And he never comes back from that until he turns into a walker…And then at the end of that, it was just Tyreese and [Sasha] who found her. Rick and Daryl and Michonne weren’t there. So it was essentially the same idea, except you saw me taking chunks out of Laurie Holden in that version.”
In the original ending, Tyreese is the one who kills Milton.
Chad Coleman's (Tyreese) take on the finale:
“Man, it was awesome. Sasha and I, we were protecting the wall and we heard these screams. We followed the screams, going through the streets with our weapons. I’ve got to kick in this door, which will probably be one of the bloopers. I went to kick the door in and I almost fell backwards down the stairs. Whoever rigged that door, they got me on that one. But, we kick in the door and finally we get to [Andrea], and it was an incredibly powerful, excruciating scene. Sasha and I are doing our best to try and comfort her before she took herself out. I thought there was some great work going on. But I was there for the revision and that was incredibly powerful, and it made all the more sense for it to be full-circle for them. But for us, it was excruciating, and it was really powerful. I hope they dig it up. I’d love to see it.”
And finally, Sonequa Martin-Green (Sasha):
“Wow, that scene was something else. Sasha and Tyreese are on guard in Woodbury, everybody’s gone to the prison to do the raid where they got defeated, and we’re back behind taking care of the people that were left behind. And we hear screaming, we hear noises, and we go and we seek it out and we find her. She’s in this torture chamber. And so we walk in and we say, ‘Oh my gosh, who did this? How did this happen? Who did this to you?’ And of course, we deduce that it was the Governor. We unchain her, we see that she’s bitten. She wants a gun. She says, ‘Give me a gun. Give me one of your guns.’ Tyreese doesn’t want to do it. He’s like, ‘No, no,’ but she’s like, ‘No, I’ve made up my mind. Give me a gun. I’m going to end this.’ It was very endearing and it was quite heart-wrenching, this scene, because to find her at that point in her life, at the end, especially we were not that familiar with her—Sasha and Tyreese, I mean—so to come to someone and to find them in the most vulnerable moment of their life, it was hard. The scene, it had a serious depth to it.
“And it was respected, the magnitude of the moment. It was extremely heavy. And we knew this was the last moments of her life, and so we were extremely respectful. Once she talked us into giving her the gun, it was her funeral. It was a memorial service to her. We handed her the gun and we let her be. There was also a moment where Sasha’s cradling Andrea in her hands after we unchain her. And it’s a to-do to get all the chains off of her, and we’re literally cradling her and Sasha says, ‘We’re not going to leave you here,’ which is a serious arc for Sasha from the first episode where she’s ready to leave Donna who is a part of their camp. It spoke to her journey and where she ended up. And she says, ‘No, I want you to give me the gun and I want you to leave me.’ And so we do, and Sasha and Tyreese stand outside of the door and hear the gun shot and share a look with each other, and that was the end of the scene. It was extremely powerful. I will say though, to be honest, I liked what happened better because it needed that. Andrea needed that goodbye. She needed to be united with her family. That was really important to show. So, I loved shooting what we did, but I love the way it ended up.”