HEBRON, West Bank  Israeli soldiers shot and killed an unarmed 65-year-old Palestinian man in his bedroom in this tense city early Friday, in what appeared to be a case of mistaken identity.

The man’s wife said he was sleeping and she was praying when soldiers burst into the apartment before dawn, entered the bedroom and immediately opened fire. Afterward they asked her for his identity card. She gave her account a few hours later, standing next to the bed, whose mattress, sheets and pillows were soaked in blood. The headboard, an adjacent wardrobe and the ceiling were also spattered with blood and bits of what appeared to be brain matter.

The Israeli military expressed regret but offered no explanation beyond saying that it had been carrying out an arrest operation. It said the West Bank division commander had been ordered to carry out a speedy investigation, with conclusions to be presented as early as next week.

The soldiers were apparently looking for the dead man’s nephew, a Hamas militant who was one of six released from a Palestinian Authority prison on Thursday. He was staying in an apartment on the floor below the slain man’s and was rearrested by the Israeli military soon after the killing. Four of the other released militants were arrested by the Israelis overnight as well.