A former Toronto IT worker, known as the “voice of ISIS” because he narrated its gruesome execution videos, is being investigated by the RCMP for “serious terrorism offences,” a court document unsealed Tuesday reveals.

The RCMP alleged in the top-secret affidavit it had reason to believe Mohammed Khalifa, a Canadian citizen captured in Syria by U.S.-backed Kurdish forces in January 2019, had committed four terrorism offences.

He remains in custody in Syria.

The evidence against him includes papers that were uncovered by the U.S. military in Raqqa after ISIS was ousted from its former capital in October 2017, the RCMP affidavit alleged.

Read more: Global News (Canada)