Laban was of the tribe of Joseph. After acquiring the Plates of Laban (1 Nephi 5), Lehi and his family studied the record. They looked over the genealogy and Nephi noted that not only Lehi’s family, but also Laban, was of the tribe of Joseph. Laban was their kinsman. Perhaps this changed how Nephi felt about killing Laban. We do not know if this family connection made it easier or harder on Nephi.
Laban was a prominent person in his community. There are several possible positions that Laban could have held in ancient Jerusalem society. His position would have then determined what, exactly, he was in charge of. Laban could have been a commander of the armies of the Kingdom of Judea. At the time of Lehi’s departure from Jerusalem, the northern Kingdom no longer existed—it had been conquered by Assyria and the Ten Tribes were scattered out of the land. Jerusalem was now a city that was teetering on extinction. Poor political choices were made aligning the Kingdom of Judea with Egypt. Egypt and Babylon were at war with each other and Babylon had already conquered Jerusalem. Although it is unknown whether Laban was part of the crowd that had attempted to kill Lehi, he may well be implicated among those who charge Lehi with the crime of false prophecy, as Urijah and Jeremiah had been charged a few years earlier (Jeremiah 26).
Perhaps in this time of turmoil, Laban was a military commander. 1 Nephi 4:22 says that Laban had been away from his home talking to the elders of the Jews. He may have been meeting to discuss what to do about defending Jerusalem—how they planned on dealing with the political, social and economic problems they were facing. That is possible. Nephi’s narrative states that Laban was able to command a garrison of fifty within the walls of Jerusalem. This is a clue that he may have held the archaeologically known title of "commander of the citadel."
Laban had distinctive armor of some kind. Every man in the community was responsible to serve in the military and be ready to go to war. There was no armory in the city where weapons and armor were issued. Everyone had to own their own armor and weapons. The rich people in the community personally owned better weapons and armor, while the poor people went without proper protection.