It is narrated from Abdullah bin Umar (may Allah be pleased with them both) that a Muslim deliberately killed a dhimmi, and the case came before Uthman (may Allah be pleased with him). He did not have him killed; rather, he imposed upon him blood money like the blood money of a Muslim.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15931
Ibn Shihab (may Allah have mercy on him) said: Sayyiduna Uthman and Sayyiduna Mu'awiyah (may Allah be pleased with them both) did not kill a believer in return for a polytheist.
The first (narration) is connected (mawsul), and this one is munqati' (has a broken chain).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15932
Al-Zuhri (may Allah have mercy on him) said: Ibn Shas al-Judhami killed one of the dhimmis of Syria. The case came before Sayyiduna Uthman (may Allah be pleased with him), and he ordered that he be killed. Sayyiduna al-Zubayr (may Allah be pleased with him) and many of the Companions of the Messenger of Allah (peace and blessings be upon him) objected to the ruling, so he refrained from killing him and fixed the blood money at one thousand dinars.
Imam al-Shafi'i (may Allah have mercy on him) said: I said: This is from the narration of someone who is unknown. If it is not established, then abandon using it as proof; and if it is established, then you yourself have claimed that he wanted to kill him but some of the Companions of the Messenger of Allah (peace and blessings be upon him) prevented him, and he deferred to them. So here are Sayyiduna Uthman (may Allah be pleased with him) and some of the Companions of the Messenger of Allah (peace and blessings be upon him) agreed that a Muslim is not to be killed in return for a disbeliever; so how have you opposed them?
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15933