The following year marked a watershed in the history for the Kingdom of the Isles with the successive deaths of David and Óláfr. The latter was slain by three Dublin-based sons of his exiled brother, after which these men—the Haraldsonnar—partitioned Mann amongst themselves. Once in control, the chronicle reveals that the Haraldsonnar fortified themselves against forces loyal to the kingdom's legitimate heir by launching a pre-emptive strike against Fergus. Although the invasion of Galloway was repulsed with heavy casualties, once the Haraldsonnar returned to Mann the chronicle records that they slaughtered and expelled all resident Gallovidians that they could find. This ruthless reaction evidently reveals an attempt to uproot local factions adhering to Affraic and her son. Whatever the case, within months of his father's assassination, Guðrøðr executed his vengeance. Enstrengthened with Norwegian military support, Guðrøðr overcame his three kin-slaying cousins, and successfully secured the kingship for himself.