The Egypt affiliate of ISIS, the Islamic extremist group, has just has released photographic evidence that purports to show the execution of a Croatian hostage named Tomislav Salopek.

An image of Salopek's decapitated body released on Wednesday strongly suggests all efforts to free him may have been made in vain. The terrorist watchdog group SITE posted a blurred-out photo of Salopek, which was first distributed on Twitter and came with a caption denouncing Croatia's participating in the war against ISIS.

The Independent reported the caption, written in Arabic, says Salopek was killed "for his country's participation in the war against the Islamic State."

Last week, it was reported, ISIS released a video identifying their captive as a 30-year-old man who was taken hostage outside of Cairo. In the video, which shows an ISIS fighter in combat gear standing before a kneeling figure, the ISIS affiliate threatened to kill Salopek within 48 hours if Egypt did not release unspecified "Muslim women" from prison.

As CNN reported, the Croatian government responded by saying it was “making all the efforts to resolve the difficult situation.”

Salopek, a father of two, was working for CGG Ardiseis, a French oil and gas company which has an office in a Cairo. He was the first foreigner to be abducted and threatened by ISIS's Egyptian affiliate organization Wilyat Sina, which translates to "the Sinai Province."

Salopek's father made a public plea for his son's life last week, saying, "I am asking the people who hold my son to let him return to his family, because his motive to go to your homeland was exclusively to earn bread for his children. Nothing else."

The Republic of Croatia has released a video statement on Twitter stating they cannot confirm whether or not the Salopek is in fact dead.

As reported in Al Jazeera, a spokesman for the Egyptian interior ministry's press office affirmed that they have seen the news online but that they "are currently making our own checks."