[Sure enough, Boone shows up in time to see Belloq on the ground with Niko stood over him. If he had his way, he would have let Niko kill him. He's here as part of patrol, though. Kay specifically sent him to stop his friend from doing something he might regret later. That means he has to stop Niko, whether he likes it or not. Of course, he doesn't know that Niko has already decided Belloq isn't worth it.]

Niko!

[He doesn't have to raise his voice much. It carries pretty well. As he gets closer he throws Belloq a disgusted look. Sure, he's stopping Niko from killing him, but he's not bothering to hide his contempt for the traitor who tried to kill his friend.]