Are the six individuals who intentionally participated in the killing and colluded in it to be considered murderers upon whom qisas should be carried out, and is the act of one of the heirs of the slain killing the seven perpetrators a legitimate qisas in the absence of an effective judiciary?

Assisting the oppressor is by preventing him from oppression. The blood of a believer is sacred to Allah, and intentionally killing him is punishable by Hellfire. The first matter to be judged on the Day of Judgment will be bloodshed. All those who conspire to kill shall be executed unless the blood relatives pardon them or accept blood money. Islamic law has not granted individuals the right to take retribution into their own hands; rather, it has made retribution the responsibility of the ruling authority. Whoever kills murderers without being the sole guardian of the blood is subject to retribution, and if he is the rightful claimant to the blood and takes his right, then the authority shall discipline him.