How old was Itachi when He killed his entire clan?

Itachi was 13 when he killed his clan.

Itachi killed his clan to Join akatsuki?! LOL!, no he killed it with the help of Uchiha madara since some of the targets were too strong, second, he kiled them all, because it was orders from the elders of the village that was given to the only ambu they thought had enough strengh to kill them all, and he didnt kill sasuke cause he loved his little brother too much and failed at killing him, when itachi runs away from the scene, sasuke throws a kunai at him, and that kunai hits itachi's head band creating that scratched simbol, and when he looks back to sasuke, he sheds a tear because, the person he loved the most, his little brother, attacked him with the intension to kill him, if you don't believe me, read the manga, or see shippuden episode 140 or so, and yeah he was like from 13, and he joined akatsuki just to work as a double agent, since he sent information about akatsuki every so to konoha, and he told the hokage NOT to tell the truth to sasuke, cause if he did, sasuke would take revenge on the village and not on itachi, and itachi wanted this because he loved his village a lot, and also, Sasuke achieves his goal to kill itachi and gets all of Itachi's mangekyou sharingan tecniques AND his own mangekyou, but after that, Uchiha Madara, the only other uchiha that wasnt killed, tells sasuke the truth about itachi, and now sasuke wants revenge on the village, ALL OF IT AND WANTS TO WIPE OUT THE ENTIRE VILLAGE OF KONOHA FOR ORDERING ITACHI TO WIPE OUT THE UCHIHA CLAN, well that's all, and sorry for going off topic but i wanted to say this just so the guy that said that itachi did it to join akatsuki know what really happened. ~By Black Ace1809~