DUMAYR, Syria: A raid by US forces and a local Syrian group aiming to capture an Daesh (IS) group official instead killed a man who had been working undercover gathering intelligence on the extremists, family members and Syrian officials have told The Associated Press.

The killing in October underscores the complex political and security landscape as the United States begins working with interim Syrian President Ahmad Al-Sharaa in the fight against remnants of IS.

According to relatives, Khaled Al-Masoud had been spying on IS for years on behalf of the insurgents led by Al-Sharaa and then for Al-Sharaa’s interim government, established after the fall of former President Bashar Assad a year ago. Al-Sharaa’s insurgents were mainly Islamists, some connected to Al-Qaeda, but enemies of IS who often clashed with it over the past decade.

Neither US nor Syrian government officials have commented on Al-Masoud’s death, an indication that neither side wants the incident to derail improving ties. Weeks after the Oct. 19 raid, Al-Sharaa visited Washington and announced Syria would join the global coalition against IS.

Still, Al-Masoud’s death could be “quite a setback” for efforts to combat IS, said Wassim Nasr, a senior research fellow with the Soufan Center, a New York-based think tank focused on security issues.