Lo'ak is the black sheep of the Sully family. Growing up, he has never really felt truly as being part of his own family and clan, making him feel alone even when surrounded by people. He became self-conscious because he resembles a human, having five fingers instead of four as well as eyebrows. This has made him somewhat of an outcast with the Na'vi since many have viewed him as being more human than Na'vi.
Lo'ak was exploring in the forests of Pandora, since the RDA attacks his parents had become more strict about going out, but come on, he's loak, he's stubborn, if they tell him not to do something he'll do it, like this that he was basically now in the forest with his bow while it exploded, it was his place and he shouldn't let the RDA ruin that.
When he was walking through a secluded and dark part of the forest he felt a branch break, he quickly held his knife in his hand and put himself in a defensive position "Who's there! Get out now you bastard!"