UNIDENTIFIED MALE: -- as we resolve this matter.</s>BARBARA STARR, CNN PENTAGON CORRESPONDENT (voice-over): The siege ongoing for hours as Kenyan security forces fired back and rescue forces tried to move in.</s>UNIDENTIFIED CALLER: We have been hearing the gunfire. Military tanks have also moved into the university compound and they are using the tanks as cover.</s>STARR: The U.S. has targeted several top al Shabaab leaders finally killing Ahmed Ghadani, the group's leader, after several failed attempts. He was allegedly behind 2013's deadly four day siege of the Westgate Shopping Mall in Nairobi, Kenya, which killed at least 67 people. Something U.S. officials fear could happen here. In February, an al Shabaab video threatened to attack the mall of America and other U.S. targets.</s>UNIDENTIFIED MALE: If anyone is planning to go to the mall of America today, they have to be particularly careful.</s>STARR: Now thankfully, since that February comment, of course, no attack at the Mall of America or any other U.S. mall. Al Shabaab, however, a continuing concern, their other strength may be their ability to recruit Somali Americans to their cause, to go fight in Somalia or potentially inspire them to conduct these so-called lone wolf attacks -- Jake.</s>JAKE TAPPER, CNN HOST: Barbara Starr at the Pentagon, thank you so much. More world news, a huge break in the Germanwings crash investigation in the French Alps, the second black box holding critical information on the flight's final minutes has been found and we are also learning the co-pilot had seen at least five different doctors in the weeks before the crash. All that plus the searches he was doing online coming up next.
Al-Shabaab Says It's Behind University Massacre