ISTANBUL (AP) A former British army officer who helped found the White Helmets volunteer organization in Syria was found dead in Istanbul early Monday, Turkish officials and the group said. The cause of death was under investigation.

James Le Mesuriers body was found near his home in the Beyoglu district by worshippers on their way to a mosque, the state-run Anadolu news agency reported.

The Istanbul governors office said comprehensive administrative and judicial investigations had been initiated into Le Mesuriers death.

Anadolu said police established that no one had entered or left his home, and they believe he may have fallen to his death.

Le Mesurier was the founder and CEO of May Day Rescue, which founded and trained the White Helmets, also known as the Syria Civil Defense, a group of local humanitarian volunteers. He was 48 and had moved to Turkey with his wife four years ago, Anadolu said.

The White Helmets confirmed his death on its Facebook page.

The family of the Syrian Civil Defense extends its deepest condolences to his family, and we express our deepest sorrow and solidarity with his family, the group said.