(RIPOLL, Spain) — They were brothers and boyhood friends from a town with no unfamiliar faces. They were linked by Moroccan roots and equally tied by their upbringings in Ripoll, an ancient hub in the Catalan foothills known for its monastery and passageways dotted with cafes and kebab shops. But most recently, police believe, the young men were drawn together by an imam and an alleged plot to murder on a massive scale — an extraordinary secret for 12 people to keep for months on end. In the suspected extremist cell’s final days, the group accumulated more than 100 gas canisters, blew up a house in a botched effort to make bombs, drove a van through Barcelona’s storied Las Ramblas promenade, and attacked beachside tourists, Spanish authorities said. The Islamic State group claimed responsibility for the attacks that killed at least 14 people and left scores wounded.