Does the retribution of "a life for a life" apply to a killer who mistakenly killed someone, with the intention of killing another person, and insistence on killing him?

If the killer intended to kill a person for whom there is no Qisas, but killed another, then Diyya is obligatory. However, if he intended to kill a person for whom there is Qisas, and killed another, believing him to be the intended target, then Qisas is obligatory if the guardians of the victim's blood demand it.

It is obligatory to reconcile between brothers and to inform the authorities if the killer is determined to carry out his act.