Jackson was a security officer in Arkham Asylum, who was among the many guards present during Joker's return to the asylum by Batman as a part of Warden Quincy Sharp's to step up security at Arkham following Joker's previous escape.
Arkham Asylum Incident
Jackson was posted in the tunnel connecting Arkham North to Arkham East along with five other Arkham security personnel during the Joker's takeover. Shortly after, the villain dispatched four liberated inmates with weapons to take the tunnel by storm. Outgunned, three of the guards began retreating back to the safety of Arkham East, but left another three more guards behind, still trapped in the tunnel, including Masked Guard #83, #84 and his close friend, Jackson. Masked Guard #83 was shot and killed by the inmates and Jackson was mortally wounded during the crossfire, but Masked Guard #84 managed to drag him to safety behind an ambulance to take cover. From this position, Masked Guard #84 returned fire on the Joker's inmates, shooting and killing two of them, likely the ones who shot Jackson and Masked Guard #83. However, Jackson soon died from his injuries, and slumped his head to the side. Kneeling by his fallen colleague, Masked Guard #84 held up his rifle and looked the body over, realizing that he was dead. Numb from shock, the Masked Guard remained staring at Jackson's corpse in near disbelief, pausing only to reload his rifle. When Batman arrived on the scene to remove the remaining armed inmates from the tunnel, he found Masked Guard #84 still sitting solemnly by his deceased friend. Turning to face Batman, the guard reported, "I can't believe it. They killed Jackson." Angry that he had not arrived in time to prevent the death of another guard, Batman responded to the only survivor in the tunnel: "Stay with your colleague. I'm ending this. Now." Although Batman successfully defeated the Joker's men and disarmed them, he did not stay to report his clearing of the tunnel to Masked Guard #84, who remained hiding behind the ambulance as the Dark Knight continued to Arkham North and continued kneeling besides Jackson's corpse.