Amr bin Shu'ayb narrates from his father, and he from his grandfather (may Allah be pleased with him), that the Prophet (peace and blessings be upon him) said: "Whoever kills deliberately is to be handed over to the heir of the slain; if he wishes he may take blood money from him, and if he wishes he may kill him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16076