Zau Seng, a member of the Kachin ethnic minority from northern Myanmar, also known as Burma, died while filming fighting outside the town of Tal Tamr, according to the Christian group he worked with, who blamed Turkish-backed forces.
A day earlier, he had recorded a rescue of several people carried out by the group, said David Eubank, the American founder of Free Burma Rangers.
"Thank you for being my brother and for being fearless in all things," he said in a statement. "Thank you for showing me how to live and for putting a light on the world. Thank you for going to another country because, as you said, others had helped you."
Turkey launched a cross-border offensive on Oct. 9 targeting Kurdish forces in northeast Syria after President Donald Trump pulled U.S. troops out.
It has denied responsibility for the attack on the FBR staff, which also injured an Iraqi interpreter.
Zau Seng had traveled to Syria and Iraq several times to treat people injured on the front lines and document abuses.
"The last time we talked was on November 1," Lu Nu, his 27-year-old widow told Reuters by phone. "It was a video call. He said he wanted to see his daughter. Then he told his daughter to behave well."
She called her husband, who had been a member of a Kachin ethnic armed group, a "military serviceman who served the people."
Zau Seng grew up amid a long-running civil war in Kachin state, the majority Christian region where ethnic rebels have been fighting for greater autonomy from the central government.
Friends said he carried out humanitarian work in conflict zones across Myanmar.
"The world lost a courageous Kachin man who lived his life serving others," said John Quinley III, a human rights specialist with Fortify Rights.
The day he died was his daughter's first birthday, which his wife marked with a prayer ceremony. In the evening, she got the news from Eubank.
"I still feel like I can’t believe it," she said."I am not sure if his body can be brought back to Myanmar but I’m urging them to bring back his ashes."