A Somali police officer arrests a suspected rebel member of the al Qaeda-affiliated al Shabaab among beach goers in Mogadishu. Al Shabaab claimed responsibility for today's pre-dawn attack on a Kenyan university campus near the Somali border. The following gallery examines who is al Shabaab. Here: Somali police officer (R) arrests a suspected rebel member (L) of the Al Qaeda-affiliated al Shabaab among beach goers at the Lido beach north of Somalia's capital Mogadishu March 23, 2012. (Photo by Feisal Omar/Reuters)

An Afghan man works at a traditional yarn factory in Heart province, Afghanistan July 28, 2015. (Photo by Mohammad Shoib/Reuters)

Ranger trainees and trainee dogs simulate an ambush against rhino poachers at the Paramount Group Anti-Poaching training and K9 (canine) academy on November 26, 2014 in Magaliesberg, South Africa. One of the largest of its kind in Africa, the Academy will address the ever increasing need for training of Conservation Officers in anti poaching activities, wildlife contraband detection, specialist K9 solutions and Ranger K9 handler training – all of which have proven success rates in combatting and apprehending poachers and their activities. (Photo by Gianluigi Guercia/AFP Photo)

This picture released by Turkish Cumhuriyet Daily newspaper shows Dilek Dundar (L), the wife of editor-in-chief of Turkish newspaper Cumhuriyet daily Can Dundar, trying to stop a gunman who is also being held back by a man on May 6, 2016 in Istanbul. Turkish opposition journalist Can Dundar escaped a shooting on May 5 outside a courthouse in Istanbul where he is on trial, adding police detained the assailant. Dundar, who was unharmed, was outside the courthouse during a break as the court prepared to deliver its verdict in his trial for allegedly revealing state secrets in a newspaper story. (Photo by AFP Photo/Cumhuriyet Daily Newspaper)

Haitian soldiers shoot in the air to try to control the crowd as they wait for food to be handed out after Hurricane Matthew hit Jeremie, Haiti, October 18, 2016. (Photo by Carlos Garcia Rawlins/Reuters)

A member of the “Castellers Minyons de Terrassa” adjusts her belt before forming a human tower or ÒcastellÓ during the festival of the patron saint of Barcelona “The Virgin of Mercy” at Sant Jaume square in Barcelona, Spain, September 20, 2015. The formation of human towers is a tradition in Catalonia dating back to the 18th century. (Photo by Susana Vera/Reuters)

Erica Bougard of the U.S. competes in the high jump event of the women's heptathlon during the 15th IAAF World Championships at the National Stadium in Beijing, China, August 22, 2015. (Photo by Fabrizio Bensch/Reuters)

Models on the catwalk Yeezy: Season 4 show, Spring Summer 2017, New York Fashion Week, USA on September 7, 2016. (Photo by Your Name/BFA/Rex Features/Shutterstock)