At least 54 people were killed Monday in Yemen’s capital city when a suicide bomber detonated a car filled with explosives at an army training camp and local militia compound. The deadly attack in Aden also injured 67 people, who were taken to a nearby hospital. Reuters reported that ISIS has claimed responsibility for the attack through its Amaq news agency—and even released an image of a smiling, waving man who it claims carried out the blast. The man is reported to have entered the compound behind a truck bringing breakfast to the trainees. “It’s a massacre,” Hakim al-Masmari, editor of the Yemen Post newspaper, told Al Jazeera, describing the bombing as having “the highest death toll” of any attack to have happened in Aden up till now. Yemen has been torn apart by an 18-month civil war between Saudi-backed government forces and its Shiite Houthi insurgency.