I would have killed them according to the statement of Allah's Apostle, 'Whoever changed his Islamic religion, then kill him" (Bukhari Volume 9, Book 84, Number 57).
Umprofethi islam sika Mohammad wathi, "Yilowo nalowo washintsha ngenkolo yakhe Islamic ke ukumbulala '." - Bukhari: Volume 9, Incwadi 84, Number 57.