ISIS militants have beheaded a world-renowned antiquities scholar in the Syrian city of Palmyra.

Khaled al-As'ad, an 82-year-old archeologist, was killed and then hung upon a column in the main square of the city because he would not reveal to the Islamic State where valuable artifacts had been moved for safety.

As reported by the Syrian Observatory for Human Rights, al- As’ad was killed with a knife before dozens of people.

The professor had committed his life to preserving antiquities.

According to CNN, Syria's director of the General Department of Antiquities and Museums, Maamoun Abdulkarim, explained that al-As'ad was killed because he refused to reveal the location of priceless archaeological treasures to ISIS during an interrogation.

"He said, 'Whatever happens, happens. I cannot go against my conscience.' He had a very strong personality and refused to yield to anyone," said Abdulkarim of the late archeologist.

ISIS posted a photo of his body on social media which showed the dead archeologist tied to a pole with a white sign over his corpse which, in Arabic, read "Heretic."

Abdalrazzaq Moaz, Syria's ex deputy minister in charge of cultural heritage, denounced al-As'ad's execution as a catastrophe. "He was a great figure, one of the most senior scholars alive in Syria," Moaz said.

Syria's antiquities chief Maamoun Abdulkarim summed up the tragedy of al-As'ad’s murder by saying, "The Syrian people are shocked because he represented Syria's culture and history."

In June ISIS shocked the world by blowing up two ancient shrines in Palmyra, an act which they regarded as sacrilegious.

As reported in the Guardian, Tom Holland, a British historian and media commentator, found the news of al-As'ad's death unnerving on a grand scale.

“For anyone interested in the study of the ancient world, it comes as -- to put it mildly -- a shock to realise that ideologues exist who regard the curating of antiquities and the attendance of international conferences on archaeology as capital offences,” said Holland.