I have spoken to many former paramilitaries, some of whom killed, and asked what motivated them. Many of them started as young as 14. They enjoyed rioting with little sense of political possibilities, but then they got hardened by their experiences of arrest and interrogation.
Or they saw the Troubles get more violent and more threatening and, by then, they were already involved in organisations which were preparing for war.
Bobby Storey was only 15 when he joined the IRA. For all that he is remembered as a hard man and a tactician, it can hardly be assumed that he had worked out his motivation as a mere kid.