article_snippet.sent: Most of the victims had been shot from behind, in the back of the head, a medic told CNN.
article_snippet.sent: The post does not say what role a man in connection with it may have played.
article_snippet.sent: Many thought measures taken after the Westgate Mall massacre had filled the gaps.
article_snippet.sent: At least 67 people died then.
article_snippet.sent: But a December attack at a quarry is the second-worst in the country's history, and a December attack at a quarry has evaporated much of the confidence won after Westgate.