It has been alleged that Abbas R. together with Raad A. joined ISIS in June 2014 in Mosul. In the same month, Abbas R. was present during the execution of two Shiite women by ISIS fighters and assisted them with the transportation of the bodies. In October 2014, he allegedly participated in the execution of a high-ranking Iraqi civil servant captured by ISIS after the group took control over the city. Abbas R, together with other ISIS members, including Raad A., allegedly escorted the captive to the execution site in Mosul and guarded him until he was executed. He is also suspected of humiliating and insulting the captive.
Abbas R., residing in Germany, has been detained since 24 May 2017, following his arrest in connection with another investigation. On 9 August 2018, he was indicted for membership in a terrorist organization and war crimes (what appears to be a complicity in unlawful killing of a person in power of a party to the conflict and possibly outrages upon personal dignity). The Berlin Higher Regional Court has not yet scheduled the trial.