Complex sentence: In contrast, a 2011 Historical Enquiries Team investigation into the incident found that Provisional IRA volunteers were responsible for the attack despite the organisation being on an official ceasefire, and found that the victims were targeted simply because of their religion.
Split into simpler sentences: In contrast, a 2011 Historical Enquiries Team investigation into the incident found that members of the Provisional IRA had carried out the attack despite the organisation being on ceasefire. It also found that the victims were targeted simply because of their religion.