X-ray apparently of Osayed Qadus' head showing a bullet lodged inside (Source: Btselem)
The Israeli military has disciplined four officers involved in two clashes with West Bank protesters in which four Palestinians civilians were killed.
The events leading up to the shootings, less than 24 hours apart, "could have ended differently", a military statement said.
Three officers have been reprimanded by military chiefs and one officer involved has been demoted.
But an Israeli rights group says the army inquiry does not go far enough.
Btselem is waiting for the results of a military police investigation into one of the incidents and pressing for another criminal investigation to be opened, a spokeswoman for the organisation said.
"The process that has been completed by the Israeli Defence Force is an internal operational debrief. The question we're raising is if these people were killed unlawfully, the proper avenue is a criminal investigation," said Sarit Michaeli of Btselem.
The investigation into the incidents near the Palestinian villages of Iraq Burin on 20 March and in Awarta the day after was carried out by Israel's top military officer, Chief of General Staff General Gabi Ashkenazi.
He has reprimanded the two commanding officers of the units involved.
One was was identified as Colonel Itzik Bar of the Shomeron Regional Brigade.
The other was only identified only as the "commander of the Nachshon Battalion".
The demoted officer involved in the Awarta killings was only identified by his former rank of first sergeant.
A deputy company commander also faced a "rebuke" for his role in the incident at the Awarta checkpoint, the statement said.
"The chief of the general staff determined that the events could have ended differently from a professional standpoint and the difficult results could have been prevented," the statement said.
The Israel Defense Forces troops were deployed to Iraq Burin to prevent demonstrators getting to the Israeli settlement of Bracha.
A military police investigation is continuing into two of the killings
The IDF said in its latest statement that the squad had been cleared to use rubber-coated bullets against the protesters, who had, according to the IDF, thrown fire bombs at the unit.
Later, brothers Mohammed and Osayed Qadus died from wounds they sustained from shots fired by the IDF.
The Qadus family told the BBC in the days after the deaths that both youths were on their way home from college, and were not taking part in the protests, when they were shot.
An x-ray of what was said to be 15-year-old Mohammed Qadus' skull, released by human rights group Btselem, showed what appeared to be a bullet lodged in his brain.
But the IDF statement said they could not establish the veracity of the x-ray.
"The IDF could not verify the autopsy and could therefore not confirm that the rioters were in fact hit by live rounds," the statement from the IDF said.
They said a military police investigation had been opened and is continuing.
"The investigation shows that the incident could have ended differently and with better results and seemingly could have avoided harm to civilians," the statement said.
In Awarta the next day, the IDF statement said, soldiers opened fire on two Palestinian men who had "begun acting suspiciously" at a checkpoint.
One then attacked soldiers with a bottle.
"According to the general officer commanding's investigation, one of the soldiers felt his life was in danger and fired at the Palestinian."
A second man raised what was described as "a sharp object" and was also shot dead by the soldiers, the army investigation said. It is not clear what the "sharp object" was.
"While the soldier, believing his life was at risk, acted subjectively, the chief of the general staff holds the officers responsible for training their soldiers to act in difficult operational situations."
In the aftermath of the incident, local Palestinians told the BBC the two men were arrested before they were killed, on the basis of a phone call a village elder says he received from the military saying they were being held, before later hearing that they had been shot dead.
The military has demoted one of the soldiers manning the checkpoint, but a criminal investigation by military police has not been launched into the events at Awarta.
Btselem said that the military "operational debrief" which led to the disciplinary action might harm prospects for a criminal prosecution in the case of Iraq Burin.
"The internal investigation becomes a forum for them to corroborate their testimonies. If indeed they acted unlawfully then talking amongst themselves is not the right way," said Ms Michaeli said.