A Washington teenager was arrested after investigators found a large cache of weapons and writings about 'mass shooting scenarios' in his home. The alleged would-be killer, who has not been named, was obsessed with 'previous mass shooters' and 'idolized' them as he hatched a chilling plot to carry out his own murder spree, cops said. The Pierce County Sheriff's Office said they descended on the boy's home in Tacoma, Washington after being notified on Friday afternoon that he was 'making threats to kill.' Following a sweep of his home on Saturday morning, authorities said they seized a 'large quantity' of...