Complex sentence: A recent Historical Enquiries Team investigation into the incident however found that it was the Provisional IRA, who were meant to be on ceasefire at the time, had carried out the attack, and that the victims where targeted simply because of their religion.
Split into simpler sentences: A recent Historical Enquiries Team investigation into the incident however found that it was the Provisional IRA who had carried out the attack, despite being on ceasefire. It also found that the victims where targeted simply because of their religion.