A "twisted ideology" drove an Israeli soldier to fatally shoot a Palestinian assailant in the head as he lay subdued in the road, states a classified Israel Defense Forces (IDF) document leaked to VICE News.

The internal investigation includes criticism of 19-year-old Sgt. Elor Azaria's actions from multiple IDF investigating military officials. Azaria shot Palestinian attacker Abdul Fatah al-Sharif with a single bullet to the head as he lay wounded on the street in the West Bank city of Hebron on March 24. The killing has polarized Israeli society and triggered a national debate about how the military should conduct itself.

The 17-page dossier states:

* The soldier said before the shooting that the subdued Palestinian "needs to die."

* After the shooting, he told a commander: "He's a terrorist, he needs to die."

* The soldier "changed his version [of events] in the different investigations," according to one investigator, telling a commander: "I shot because I felt there was a threat to life."

* The incident "severely hurts the IDF and Israel's image."

Last week Israeli prosecutors filed manslaughter charges against Azaria, but there has been an outpouring of support for his actions from some parts of Israeli society.

The incident has pitted the military's chief of staff and defense minister, who criticized the soldier's actions, against politicians, the soldier's relatives, and sympathizers who say his actions were entirely appropriate and should be celebrated.

The criminal case is expected to hinge on whether Azaria can persuade the court that he shot the assailant because he posed a danger, rather than as an act of revenge.

The report, titled "Investigation into the incident of a terrorist attack of the Jilber Position and the subsequent shooting of the terrorist after he was neutralized," is likely to play a pivotal role in the case. When contacted by VICE News, an IDF spokesperson declined to comment on the report.

"The prosecution started out talking about a murder charge, now they are down to manslaughter," Benjamin Malka, one of the lawyers representing the soldier, told reporters earlier in April. "We are sure of his innocence and we are sure this charge will also disappear."

Azaria — who was a company medic — arrived at the checkpoint in Hebron minutes after two Palestinian assailants had stabbed and wounded another soldier on March 24, the document states.

Sharif had carried out the attack with another man named as Ramzi Aziz al-Qasrawi, who was also shot dead. An army statement on the day of the attack disclosed that: "Two assailants stabbed an [Israeli] soldier at a military post in Hebron. Forces responded to the attack and shot the assailants, resulting in their deaths." Azaria later claimed that he shot Sharif dead as he lay wounded because he feared he had been wearing an explosive vest.

The leaked investigation states that both assailants had already been checked by another soldier to ensure they "were no longer a threat." Azaria arrived on the scene at 8.21am, after this process had been completed, according to the report.

About six minutes after the arrival of Azaria, the company commander noticed head movements in Sharif, and was "surprised" to see that he was still alive.

"It is important to emphasize that until that stage, according to the understanding of the company commander, the terrorist was not moving and he assumed that he had died from the shooting of the soldiers in the incident, similarly to the second terrorist," the report states.

The company commander then "tried to contact the company situation room in order to update them on the status of the second terrorist."

According to the report, "a few seconds before the attack, few seconds before the attack, as came up in the investigation with Sergeant M, [Azaria] told him that 'a terrorist that wounded their friend needs to die.'"

The document continues: "Sergeant M tried to calm the soldier down telling him, 'Relax, our wounded friend will be just fine.'"

Azaria then "fired a single shot towards the head of the terrorist and hit him," the report says.

The company commander then took him to one side. "Azaria was agitated and told the company commander the following sentence: 'He's a terrorist, he needs to die,'" according to the report.

Azaria "changed his version [of events] in the different investigations," according to one investigating commander in the report.

"To his commanders he said right after he shot that 'A terrorist who hurt our soldiers shouldn't stay alive,'" states the investigator. "He said the same to his friend, another soldier, seconds before the shooting.

"To me... he gave a different version: 'I shot because I felt that there was a threat to life. There was a knife next to the terrorist and also people shouted that he had a bomb on him.'"

Both attackers had already been checked for additional weapons, according to the investigation. The first emergency squad that arrived at the scene, "checked whether the terrorists were carrying any weapons on them and made sure that they were no longer a threat."

"The facts speak for themselves," writes one of the investigators. "The company medic took the decision to shoot the terrorist due to a twisted ideology."

The investigators are also sharply critical of the failure to provide medical treatment to Sharif.

"The treatment of the terrorist was bad," wrote a different investigator. "We need to address the subject of treating terrorists after they get neutralized immediately. We need to increase our moral attention to it and we need to demand our soldiers do exactly what we expect them to do in such events."

Other contributors to the investigation noted that the incident had the potential to do significant damage to the IDF's image.

One wrote that, "there is no choice but to denounce and condemn it entirely."

"Incidents such as these harm the strength and power of the IDF and leave a stain on our daily activities," he added.

A fourth investigator wrote that the event "severely hurts the IDF and Israel's image."

The fifth and most senior investigator wrote: "I want to emphasize that the shooting at the terrorist while he is on the floor with almost no movement, and is bleeding for a few minutes after the terror attack happened, is a significantly immoral action and there is no good explanation for this... The shooting serves the Palestinian claims about executions and by this hurts the legitimacy of our actions."

He added: "I expect and order in the clearest way that the IDF forces in the West Bank will do their best to ensure medical treatment to every Palestinian including terrorists that [have] attacked and [have] stopped being dangerous."

If Azaria is found guilty, he faces a prison term of up to 20 years. Since 2000 only one Israeli soldier has been convicted of manslaughter, for the killing of British activist Tom Hurndall.

Statistics compiled by Yesh Din, an Israeli human rights group, based on official army figures, show that of 2,600 investigations opened by the IDF into alleged crimes committed by soldiers against Palestinians between 2000 and 2014 only 5 percent resulted in indictments. In that time frame there were four convictions against soldiers for negligent killing — which carries a maximum sentence of three years — in the case of Palestinian fatalities, and one conviction of manslaughter for Hurndall's death.