Good question. I always imagined that he was giving Justin’s father a chance to plead his case, while at the same time being able to explain his own side and maybe add more depth to explaining Justin’s failed efforts in class. I also think there was a possibility that Justin’s father would have succeeded in convincing him to give them another chance now that he had somewhat cooled off from his initial anger.

In any case, the motive for this killing was always a bit of a stretch to me. Otherwise, and despite that, it's a great episode. I wanted to provide a link to an excellent analysis of this particular episode, but unfortunately the website is down, hopefully not indefinitely.