Complex sentence: All of the MRTA members involved in the crisis were reportedly killed during the raid; however, it is alleged that several of the aforesaid members had survived the initial raid and were extrajudicially executed hours after the raid began.
Split into simpler sentences: All of the MRTA members involved in the crisis were reportedly killed during the raid. It is alleged that several of the aforesaid members had survived the initial raid and were extrajudicially executed hours after the raid began.