PARIS -- A French official has told The Associated Press that a man and a teenager who appear in an Islamic State of Iraq and Syria (ISIS) video showing the killing of a Palestinian have been identified as French citizens.

The official, who has close ties to intelligence services, also said authorities were investigating whether the man has links to the family of Mohammed Merah, the Islamic extremist who attacked a Jewish school and paratroopers in southern France in 2012.

The video, which surfaced Tuesday, shows the young teenager appear to shoot the Palestinian man in the head. CBS Radio News correspondent Robert Berger reported that Israeli officials and family members confirmed the slain man was 19-year-old Muhammad Musalam, from East Jerusalem.

They confirmed that Musalam went missing, but denied the ISIS claim that he was an Israeli spy.

The adult ISIS militant in the video speaks with a southern French accent and looks like Mohammed Merah's 30-year-old step-brother, Sabri Essid.

French authorities have not confirmed the identities of either of the ISIS militants in the execution video, but CBS News has compared the man in that video to older clips of Essid, and there is a strong resemblance.

Some French media reported that the teen who is shown firing the weapon is Essid's stepson, who would be 13.

French newspaper Journal du Dimanche (JDD) reported in May that Essid had gone to Syria with his wife, her then 12-year-old son, their infant twins and a new-born baby.

CBS Radio News correspondent Elaine Cobbe said Essid is known to American law enforcement agencies because he was arrested in 2006 on the Iraqi-Syrian border, along with another man. He was convicted of "criminal association with a view to committing terrorist acts" in 2009 in Toulouse and given a 4-year sentence.

Another investigation into his activities was opened in Sept. 2013, but he fled to Syria with his family before the French police could get to him.