They can be set to oppossing teams and they should attack each other when in range.
entity["sarah"].team = "player";
entity["goblin"].team = "enemy";
Puts Sarah NPC and Goblin NPC on opposing teams and so when in proximity they should fight.
Just note, they will only fight if their behavior leads them into range, they wont just immediately make a direct path for an enemy....their behavior must naturally lead them within range where their attack detects an opposing team member.
Of course, you can force it to a degree using scripted movements but just note you will need to do that extra step as well.