Why did Shisui Uchiha Kill himself?

Deidara, throughout the entire Naruto series after he joins the Akatsuki, has a grudge agenst Uchiha Itachi, and all uchihas, because Itachi is the one who made Deidara join the Akatsuki in the first place. Deidara, while fighting Uchiha Sasuke in Shippuuden, chewed and ate some of his clay turning himself into a human bomb in order to kill Sasuke. He blew himself up but, unfortunately, instead of killing Sasuke, Deidara killed himself.