That migth seem comolex at first glance but when you break it down it becomes much less so. (1) You killed him, meaning he must leave the system or log off. and cannot re-engage you for four hours. (2) You were killed in a group battle with his teammates, you must leave the system or log off, and cannot re-engage them for four hours. (3) You logged off, meaning that he could return to the system, no rules broken. (4) You logged back in, now if only the fighter that landed the killing shot had left and the other combatant was still in system, then yes you broke a rule by not immediately undocking and leave the system, if however they had both left, then no rule was broken.
Remember the 4 hour rule and the leaving system rule applies against you for all members of a group fight that were involved with your death, not just the one who landed the killing blow.
Saint Del is considered a holy healer of diseases of children, but also as a protector of cattle.