Question: Who opened the gate in the prison walking dead?

Disambiguated questions and answers:
context: Outside the prison, an unidentified individual lures a group of walkers towards the prison, breaking open the front gate's lock to allow them inside.
question: From the viewer's persepctive, who opened the gate to the prison, at the beginning of the walking dead's "Killer Within" episode?
short_answers: an unidentified individual
wikipage: Killer Within
context: Zack Handlen, writing for "The A.V. Club", wrote that "things become sort of uncomfortable" in the scene in "Sick" where Rick chases Andrew into a courtyard full of zombies and locks the door, noting that while Rick does not actually kill Andrew, "it's a cold, cruel move, and it indicates a growing chill in Rick's character". Lesley Goldberg of "The Hollywood Reporter" noted that in "Killer Within", Rick's decision to lock Andrew out "amid a sea of walkers came back to bite the group in a major way". Glen Mazzara felt that this decision would haunt Rick, as Rick "believed he was committing an act of murder to save the group and that murder led to deaths within his own group and forced his own son to put down his mother". "Los Angeles Times" columnist Laura Hudson considered the identity of the mysterious figure breaking open the lock on the prison gates to be "not that much of a "mystery" if you consider how many black guys there are running around outside the prison with vendettas against Rick (note: one)". Ted Pigeon of" Slant Magazine" described the episode's opening sequence: "With its dreamlike, foggy setting and a conspicuously waist-down perspective of the saboteur, a peculiar sense of disconnect underlines the implications of what's being depicted. The scene ends with a single close-up of a heart placed on the cold cement. It's a foreboding image that gains magnitude as "Killer Within" gives way to a sudden strike of tragedy. Moreover, the pre-credit sequence lends insight into how the episode amounts to a particularly poignant, if also problematic, entry in the show's run." Pigeon also notes that the opening segments of the episode "establish the origins for the ensuing chaos while going to painstaking lengths to conceal the identity of the man that caused it". HitFix writer Alan Sepinwall commented on Andrew's sabotage of the prison: "on the one hand, it helps justify Rick's decision to chase after the little guy in the first place. On the other, it seemed like an overly-elaborate plan from someone who probably would have been better off just leaving once he managed to get the gate open." Bex Schwartz wrote in her review for "Rolling Stone" magazine that when Andrew ("the tiny prisoner") tries to get Oscar to shoot Rick, "Oscar shoots Andrew instead, because Oscar understands life and death and remembers that Andrew was one of the bad dudes". Moore commented on how Andrew died in the series: " It's weird because I have so much fun playing bad guys and I loved the way Andrew went out! He went out like a G, and he took a few people with him! [...] Die Hard "TWD" fans will remember my character forever because of all the trouble he caused. Plus Andrew almost got Rick! The fight scenes were great! Especially in my death scene."
question: Who is the character that is discovered to have opened the gate in the prison walking dead?
short_answers: Andrew
wikipage: The Prisoners (The Walking Dead)
context: Andrew was portrayed by actor and rapper Markice Moore. He had originally auditioned for the pilot episode for the role of T-Dog, which went to IronE Singleton. Moore was later cast on season 3 as Andrew through his agency: "Production was very hush hush about season 3 so I didn't even know I booked it officially until a week before shooting. I was elated; I couldn't believe it when my manager, Gail Tassell called to tell me the good news. I'm a huge fan of the show, it's my favorite show on TV, so yes it was a dream come true." Per Glen Mazzara, "Andrew is really Tomas' right-hand man. These guys are really the ones who have been intimidating Axel and Oscar."
question: Who is the actor that is discovered to have opened the gate in the prison walking dead?
short_answers: Markice Moore
wikipage: The Prisoners (The Walking Dead)

Long-form answers:
knowledge: content: Outside the prison, an unidentified individual lures a group of walkers towards the prison, breaking open the front gate's lock to allow them inside.
wikipage: Killer Within
long_answer: Outside the prison, an unidentified individual lures a group of walkers towards the prison, breaking open the front gate's lock to allow them inside. There, they find Andrew (Markice Moore), whom Rick had left for dead, as the instigator. Andrew is about to kill Rick when Oscar shoots him, and then turns the gun over to Rick. They stop the generator and disable the alarm.
knowledge: content: "Killer Within" is the fourth episode of the third season of the postapocalyptic horror television series The Walking Dead.
wikipage: Killer Within
long_answer: From the viewer's perspective, an unidentified individual opened the gate to the prison at the beginning of The Walking Dead's "Killer Within" episode, the fourth episode of the series' third season. The character Andrew, portrayed by actor and rapper Markice Moore, is discovered to have opened the gate in the prison.