Not Spanish Harlem - Washington Heights, a different neighborhood in upper Manhattan - actually farther up than Spanish Harlem. It is known for its large Dominican population.
My, how things have changed! My father grew up in Washington Heights when they were Irish/German/Jewish, etc. Of course, that was nearly a century ago. My own, limited, Manhattan experiences end somewhere around 86th Street.
Whatever problems there may be with the Dominican community, I don’t think they’re into terrorism. I DO think this guy, at least within that community, was a lone wolf nutjob.