Abouyaaqoub was believed to be the lone attacker on the run by Sunday, but authorities hadn't confirmed his identity because they were having difficulty identifying the remains of at least two extremists who died Wednesday in an explosion at a house in Alcanar where explosives were being prepared. The explosion destroyed the house, but police found remnants of over 100 butane gas tanks and materials needed for the TATP explosive, which has been used previously by Islamic State militants.