In any modern culture, if he hunted them down it would not be self-defense.
Obviously we don't have all the facts, but from the meager location details, it seems as though he did not "hunt them down." The attackers were found at different distances from the crime scene, varying by the degree of injury. This seems to suggest that the altercations took place inside the apartment, and that the attackers attempted to flee after being wounded - the one who was stabbed in the heart only made it to the stairwell, the one who was stabbed in the leg made it all the way out to the street before bleeding out. The fourth one probably sustained minor or no wounds and was able to escape completely. Too bad we don't have location info on Mr. Punctured-lung.
Cut the tiny testicles off of both of these rich, out-of-touch sumbiches, crush kill and destroy the Electoral College, wipe clean from the Earth the stain of our corrupt politicians, and elect me as the new president. --Vash