anti-terrorism efforts and part after peacekeeping force from somalia from the african union. this is a way obviously to get act at them, pure terror, pure and simple. and they won't succeed. >> reporter: this attack is outside the normal scope of operations by the al qaeda affiliate al-shabaab which claimed responsibility for the attack though it has not been independently confirmed. this group al-shabaab is more known for suicide bombings at the border of somalia. martha. martha: the questions who is involved and where do attackers come from and potentially from the united states. >> reporter: federal law enforcement sources that the fbi and intelligence community are aggressive drilling down on alleged shabaab members and whether they are american citizens this includes a scrubbing of travel records. the group released on the twitter page a list of alleged attackers. half came from western countries including the u.s., canada and