A reservist soldier suspected of killing a man he had apparently mistaken for a terrorist during a shooting attack in Jerusalem last week was arrested Monday by Military Police, the Israel Defense Forces said.

Staff Sgt. (res.) Aviad Frija was one of two off-duty troops who responded to a terror attack at a Jerusalem bus stop on Thursday, shooting at the two assailants but also at Yuval Castleman, an armed civilian who had also opened fire first at the terrorists.

Frija, who opened fire at Castleman after he had put his gun down and was holding his hands in the air, was questioned under caution on Sunday, and had his weapon taken away.

The IDF said his detention was a “preliminary arrest” and his interrogation would continue on Monday.

Frija was arrested after interrogators found discrepancies between his initial testimony and the account he provided in the Military Police questioning.

The second soldier involved in the incident, who opened fire and was injured, was also questioned under caution on Sunday.

“The IDF expresses sorrow for the death of the late Yuval Doron Castleman, who acted with courage and heroism, and engaged and eliminated terrorists in the attack in Jerusalem,” the military said in a statement on Sunday evening.

Three other people were killed and five were injured in the attack. Castleman was driving on the other side of the street when the attack occurred; he stopped his car, crossed the road and rushed at the terrorists with his firearm and fired at them.

The soldiers, who arrived at the scene at the same time, apparently mistook Castleman for a third assailant, and at least one, Frija, fired at him.

Graphic video from the scene showed Castleman throw away his gun, fall on his knees and raise his hands in the air while shouting, “Don’t shoot” as the soldiers approached him. He was then shot again.

According to additional details reported Sunday, Castleman also yelled at the soldiers until he collapsed, “Look at my ID, I am Jewish.”

Following the Military Police investigation, the IDF will decide if criminal charges can be brought against Frija. IDF protocols do not allow soldiers to shoot someone who raises their hands in the air, and officials say the soldier’s conduct during the incident was not what was expected of him based on the norms and values of the military.

Moshe Castleman, his father, said that the soldier responsible “carried out an execution,” and demanded a thorough investigation.

Yuval “did everything he needed to do so they could identify him. He went down on his knees, opened his jacket to show he didn’t have any explosives on him, yelled at them, ‘Don’t shoot, I’m Jewish, I’m Israeli,’ and they continued to shoot him,” he told Army Radio, adding that Yuval was shot in the jaw and chin, which would have impeded his ability to call for aid.

Prime Minister Benjamin Netanyahu spoke to Moshe Castleman on Sunday, after he was criticized for saying the previous evening, “The reality of armed civilians is that many times it saves lives and prevents a big disaster. In the current situation, the policy should be continued.

“We may pay a price for it, that’s life.”

Times of Israel staff contributed to this report.