The comprehensive summary here says, "Seeing his daughter ravaged by the poison, Creon chooses to die by her side by dramatically embracing her and absorbing the poison himself," suggesting that Creon willingly committed suicide. However, the play itself says, "Everyone was afraid to touch the corpse. We had what had happened to teach us. But her poor father, still unaware of the calamity, suddenly came into the house and fell upon the corpse." True, Creon's lamentations suggest a willingness to die, but the text itself doesn't imply that his death was a suicide.