ISIS released a video on Tuesday that it claims shows the execution of East Jerusalem Palestinian Muhammad Musallam, 19, who was taken hostage as an alleged Israeli spy three months ago in Syria.

The video, published by the group's Furqan media outlet, showed Musallam sitting in a room wearing an orange jumpsuit, talking about how he had been recruited and trained by the Israeli intelligence service. He said his father and elder brother had encouraged him. After that, it showed Musallam being escorted to a field and executed by a boy, described by an older, French-speaking fighter as one of the "cubs of the caliphate".

The clip, which was approximately 13 minutes long, showed Musallam on his knees as he listened to the older fighter speaking the verdict in French. Then the boy, wearing a military uniform and armed with a pistol, stands face to face with Musallam and fires one bullet into his forehead. Musallam crumbles, then the child shoots him three more times and chants "Allahu Akbar!" (God is Greatest).

In the video, Musallam repeated what he said last month in an interview published by the group's English language magazine Dabiq, in which he said he had joined ISIS to report to the Israelis on weapons caches, bases and Palestinian recruits. Israel and his family denied that he was an Israeli spy. "I tell my father and my son: Repent to God. I say to the spies who spy on Islamic State: You will not be successful, they will expose you," Musallam said in the latest video, in Arabic.

Still from ISIS’ video claiming to show the location of Musallam’s family home in East Jerusalem.

Last month Musallam's family confirmed to Haaretz that their son had traveled to Syria to fight for ISIS. The jihadist organization later published an article about Musallam in its magazine Dabiq titled "Interview with a spy working for the Israeli Mossad."

Musallam had lived with his family in East Jerusalem. He completed 12 years of schooling and even worked as a national service volunteer with the Israeli firefighting services. His father, Said Musallam, told Haaretz that his son told him three months ago that he was traveling to a course in the city of Rishon Letzion, and asked him for money.

"He left that morning and the next day I tried to call him and the telephone was turned off," said the father. "I thought that maybe he was busy. After a week we got an email that he wanted to be a martyr and he was giving up everything in his life and his family."

A still showing a child taking part in ISIS' alleged execution of Muhammad Musallam.