Story highlights Official: Al-As'ad paid with his life for refusing to reveal location of ancient treasures

Khaled al-As'ad was beheaded in the public square in Palmyra, a human rights official says

He was a professor and former general manager for antiquities and museums in Palmyra

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(CNN) Khaled al-As'ad spent his life on the painstaking task of preserving antiquities, saving the relics of our ancestors for generations yet to come.

He was working in Palmyra, a Syrian city full of ancient monuments and temples -- a city that was, in the second millennium B.C., a caravan stop for people making their way across the desert.

But over the past month al-As'ad, 82, ran into a very modern menace -- ISIS, the most brutal terrorist group in recent memory.

Khaled al-Asaad in front of a rare sarcophagus dating from the first century.

And on Tuesday, he was beheaded in the public square of the city whose heritage he had worked so hard to save, said Rami Abdulrahman of the Syrian Observatory for Human Rights.

Al-As'ad, a university professor and the former general manager for antiquities and museums in Palmyra, was decapitated as militants watched, Abdulrahman said, citing al-As'ad's relatives in the city.