Talq bin Habib (may Allah have mercy on him) said: "So let him not exceed limits in killing" [Surah al-Isra': 33] means that only the killer is to be killed in retaliation, and then his body is not to be mutilated.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15888