Daniel Salazar was born and raised in 1943 in the war-ridden El Salvador. As a child, he witnessed the brutal nature of civil war in El Salvador, and was present when many members of his village were forcefully abducted by the military, later to be murdered with their corpses being washed up a river. An unknown man coerced him to mortally shoot one of the survivors, which became his first out of many kills and an event leaving him traumatized that still haunts him even after decades. It is likely that this event led to his involvement with the Salvadoran junta. In his adulthood, he was coerced into the notorious Sombra Negra, a highly-confidential and extremely brutal pro-junta vigilante death squad who is directly backed by the CIA to carry out ruthless extra-judicial tortures, assassinations and murders in the Salvadoran Civil War. He became proficient in combat, murder and torture due to his professional trainings and battlefield experiences, something he is obviously not proud of as he didn't have a choice when he was enlisted. While torturing Adams, Daniel suggested that he was often put into the position of choosing whether he would be the torturer or the tortured in a situation. His inner lips were also tattooed with the mark of the squad as seen in "100". During this time, he met his wife Griselda, who was hardened by the war as he was, and helped keep him stable after the horrors of what he did. Daniel himself reveals that he killed around 96 people in El Salvador and still suffers the trauma of his actions.
Although it is unknown exactly what happened to El Salvador after the apocalypse, Valery Vashchenko states that the lights disappeared from the rest of the world, thus meaning it became overrun at some point during the outbreak.