Al-Shabab published images of their attack on US forces in Lamu, Kenya. What is behind the attack?

Sunatimes.com - Head of Al Shabab operation Abdulaziz Abu Musab says in an interview to the militants radio, Al Andalous, that the Simba Camp attack in Lamu was in retaliation of Kenyan anti-terror forces destruction of Hormuud offices and false boun