Surveillance video shows the deaths of two Palestinian teens, allegedly killed by live ammunition from Israeli security forces. (YouTube/Defence for Children Palestine)

A preliminary investigation by Israel suggests that its security forces fired live ammunition during a violent demonstration in May in which two Palestinian teenagers died, according to Israeli media reports Wednesday.

The deaths — caught on a surveillance camera — created a furor because Israeli forces initially denied Palestinian claims that live ammunition had been used to quell the protest.

If the use of live ammunition is confirmed, it could mean that Israeli troops and their commanders on the scene may have lied to investigators or attempted a coverup.

A border police officer has been arrested in connection with the death of 17-year-old Nadim Nuwara, said Micky Rosenfeld, a spokesman for Israeli police.

There have been no arrests in the death of Muhammad Salameh, the other teen. A third teen survived a bullet that entered his chest and exited his back during the May 15 protest at a military checkpoint between Israel and the West Bank.

An Israeli border police officer arrives at a hearing Wednesday at the Magistrate Court in Jerusalem. Israeli police arrested the officer in the fatal shooting of a Palestinian teenager in May. (Ronen Zvulun/Reuters)

Palestinian officials, human rights activists and the families of the teens have insisted that the youths were shot in cold blood by Israeli security forces, which critics claim are too quick to fire on civilians and then try to cover up their actions.

After the incident, State Department spokeswoman Jen Psaki called for a thorough, transparent investigation of the case, which has been one of the most widely documented and debated in Israel in years.

On Wednesday, Siam Nuwara, the father of Nadim, praised the Israelis for the arrest. “I know Israel is a country of laws,” he said. “This is a golden opportunity for Israel to prove to the world that its laws are not only for them but for Palestinians, too.”

Details about the arrest of the officer and the investigation were not released. An attorney for the officer told reporters during a courtroom appearance that his client maintains that he had discharged rubber bullets only.

One reason for the delay in the investigation, Israeli officials say, is that the Nuwara family turned over bullet fragments for ballistic tests only in September.

The arrest comes at a time when East Jerusalem neighborhoods, including the Old City and its religious sites, have been roiled by frequent clashes between rock-throwing Palestinian youths and Israeli police.

In the past month, Palestinian drivers have killed four Jewish civilians in two attacks on the Jerusalem light rail. On Monday, Palestinian assailants carried out two deadly knife assaults.

Both Israeli and Palestinian leaders accuse the other side of incitement.

Immediately after the May incident, Israeli police and military officials said that they had no evidence that live fire was used and that their officers had responded to rock-throwing and tire-burnings with standard crowd-dispersal methods, including tear gas and rubber bullets.

Israeli Defense Minister Moshe Yaalon said at the time that it was possible that the video had been doctored, though he did not explain how the two teens were killed.

The Israel Defense Forces asserted that the video was “edited in a tendentious manner” and “does not reflect the level of violence that occurred at the disturbance.”

A former Israeli ambassador to the United States, Michael Oren, told CNN in May that he suspected the deaths of the teens may have been staged.

“The way the bodies fall, the fact that there’s no blood — someone who was hit in the back and a bullet has an exit wound, there is a tremendous amount of bleeding,” Oren said. “There’s no bleeding in the picture. There are many, many inconsistencies.”

The video shows that the teens were felled by a single shot each, slumped to the ground and were carried to a waiting ambulance.

The surveillance camera was located in front of a warehouse owned by Fakher Zaid, a Palestinian construction contractor, that faces the road to the checkpoint.

Zaid said in an interview after the incident that the youths were throwing rocks and that the soldiers responded with tear gas and rubber bullets. But at the time of the shooting, he said, the protesters no longer posed any threat to the soldiers, who were a hundred yards away.

“They were not really doing anything. They were just standing in front of my place,” said Zaid, who claimed he was present when the teens were shot. “I think they were killed in cold blood.”

Lt. Col. Peter Lerner, a spokesman for the Israeli military, said live fire is allowed only under life-threatening circumstances. “It is based on an individual’s understanding of the threat,” he said. Because soldiers are issued body armor and face protection, Lerner said, a rock is generally not considered life-threatening, though gasoline bombs often are.

A team of medical examiners, including forensic experts from Israel and the United States, exhumed and performed an autopsy on the body of Nadim Nuwara and concluded that the 17-year-old was shot by a live round and that the bullet entered his chest, exited his lower back and caused massive internal bleeding.

“He died of a gunshot wound. The medical evidence is beyond dispute and the conclusion of the medical examiners unanimous,” Abd Alghani al-Ewawy, the Palestinian Authority’s top prosecutor, said in a June interview. He provided a summary of the autopsy to The Washington Post.

In the autopsy, the medical examiners found fragments of a bullet inside the victim. Nadim’s father collected another piece of the bullet that he said he found in his son’s bloodied backpack after it passed through his body.

Nadim’s death is unusual in that he came from the middle-class West Bank city of Ramallah, not a refugee camp, like many of those involved in routine confrontations with the Israeli military. He was headed for college, and his family is not political.

His father described Nadim as a popular kid who loved basketball and Lil Wayne. On a bookshelf in the teen’s bedroom was an English-language book, “America’s Presidents.”

Siam Nuwara said he knew his son was going to join a rally at his elite prep school commemorating the Nakba, or “catastrophe,” when Palestinians remember those displaced when the state of Israel was created in 1948.

“He was spontaneous. He would do things that no one else would do,” the father said. “None of my other children will ever be able to fill his shoes.”

Siam Nuwara said he did not know his son would go to the checkpoint. Asked whether his son was likely to have thrown rocks at the Israeli troops, the father shrugged and said, yes, he assumed Nadim did.

“The Israelis never imagined that we would agree to have his body exhumed and an autopsy done. They never thought we would find the bullet in his backpack,” Siam Nuwara said.

Sufian Taha in Ramallah contributed to this report.