What happened to Shishui Uchiha? In Naruto anime, though at first Itachi was accused for murdering his best friend, Shishui Uchiha. But later, it was revealed that Shishui gave one of his eyes to Itachi. But the next day, he was found dead. But what happened to Shishui? Did Danzo kill him?  But he already snatched his other eye before Shishui met Itachi. I did not understand if it was shown in the anime.
You can search on the wiki about the character..



What you have seen in the anime, contains more story than in the manga.
The only thing that we learned from the manga was that, Shisui gave one of his eyes to Itachi because Danzo had the other eye already. In order to hide his other eye from Danzo, he found Itachi and gave him the eye.

The truth about his death is as explained (from the wiki):


  Fearing that Danzō was right in Shisui's inability to stop the
  Uchiha's revolt and that the elder would continue to pursue his left
  eye as well, Shisui entrusted it to Itachi, telling him to protect
  both the village and the Uchiha name. Shisui wrote a suicide note
  telling his clan he cannot follow through with the coup d'etat, but
  his clan's narrow mindedness made them unable to understand this,
  believing he would even sacrifice innocent lives for the sake of the
  Uchiha Clan. The contents of the suicide note also made it appear as
  though he had crushed his eyes when jumping off a cliff into the Naka
  River to kill himself in order to prevent conflict from arising over
  his eyes within the clan. He, at the same time, was able to erase
  his existence, leaving no corpse behind. In the anime, Shisui
  was also hoping to use his death to awaken Itachi's Mangekyō
  Sharingan, succeeding in the goal.