The former United Nations Special Rapporteur on arbitrary executions and renowned human rights law professor Christof Heyns passed away this weekend.

“It is with great shock, bereavement and sadness that the Faculty of Law at the University of Pretoria has received the news of the passing today of one of its internationally esteemed and stalwart colleagues and friends,” said a tweet from the university on Sunday.

Heyns served as the United Nations Special Rapporteur on extrajudicial, summary or arbitrary executions from 2010 until 2016.

In that role, he examined mobile phone footage of Sri Lankan soldiers executing Tamils who had been stripped naked, blindfolded and shot in the head, describing the footage as “authentic” and “textbook examples of extrajudicial executions”. His report was presented in 2011, just two years after the atrocities had taken place.

"It's very rare that you have actual footage of people being killed," Heyns told The Associated Press. "This is different from CCTV. This is trophy footage."

He added that the video showed "definitive war crimes" and said "there is a prima facie case and it should now go to the next level,” echoing calls for an international investigation.

See more from the BBC here, Reuters here and the UN here.

Earlier this year, Heyns was one of a number of former UN officials and international experts who called for Sri Lanka to be referred to the International Criminal Court; for UN member states to “to pursue justice through universal or extraterritorial jurisdiction”; and for “targeted sanctions against credibly alleged perpetrators of international crimes”.