Tristan has been acting within his right to slay who he must for the protection of all. He has nothing to fear from the hunters, and no idea [i]what [/i]Nin is doing or why. 

He climbs down to approach the hunters, showing his bow but keeping his arrows in his quiver. The bow shows his purpose - but keeping the arrows sheathed shows he means no threat. 

Of course he's no threat. They're here to deal with more than he can muster.