The White Helmets emerged in 2013, working to rescue civilians in many rebel-held areas. The killers also stole two cars, phones, and walkie talkies among other things from the center.
The White Helmets rescuer, who a year ago pulled a baby girl from the wreckage of an airstrike in a dramatic scene that brought a BBC news presenter to tears, is among seven volunteers who have been shot dead in Syria.
UOSSM call on all concerned parties, the worldwide community, and human rights organizations to conduct a full investigation into this heinous crime.
The White Helmets says seven members of their rescue group were shot and killed by unidentified gunmen at the organization's office. UOSSM staff extend their deepest condolences to the families and loved ones of the victims.
It was active in rebel-held eastern Aleppo before the territory was seized by forces loyal to President Bashar al Assad.
They work exclusively in rebel-held areas and receive donations from several Western governments, including Britain, Germany, the Netherlands, and the United States.
President Bashar al Assad's government, meanwhile, accuses the group of faking videos and being a tool of its global donors.
They are known for their daring rescues, filmed and circulated on social media.
The Syrian Civil Defense called for northern Syrian checkpoints to detain any vehicles bearing the White Helmets logo that were not verified.
The town is also located some 50km from the provincial boundary of Deir Al Zor province, Daish's last major foothold in Syria and a major target for the Syrian government.
It now has over 3,000 volunteers conducting rescue missions across rebel-held parts of Syria.