Pete Reed, Global Outreach Doctors’ operations director in Ukraine and a US Marine Corps veteran, died Thursday in the Ukrainian city of Bakhmut. Reed tended to the wounded and helped evacuate the city

During the operation, Reed’s ambulance was hit by Russian shells, the Daily Beast reports. The sadness is great. “He was the good kind of nutcase. He was constantly selflessly putting himself in danger to help other people,” his brother Chandler Reed is quoted as saying.

Reed worked as a medic for the Kurdish peshmerga and Iraqi special forces as they fought to retake the city of Mosul from the terrorist organization IS in 2017. Global Response Medicine called him the “backbone” of their organization on Twitter.