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)

A military police officer aims his gun to a demonstrator during a protest in Brasilia, Brazil, Tuesday, April 7, 2015. The officer had picked up a bottle that was thrown towards them but did not fire his gun and backed away. Thousands of workers have staged rallies in 12 cities across Brazil to protest against a proposed law that would allow companies to outsource their labor force. (Photo by Eraldo Peres/AP Photo)

A woman takes a selfie next to a model of Thor during the Middle East Film & Comic Con (MEFCC) in Dubai, United Arab Emirates, Saturday, April 11, 2015. (Photo by Kamran Jebreili/AP Photo)

Deputy community chief of Yeneka village Douglas Oguta poses for a portrait in his home on the outskirts of the Bayelsa state capital, Yenagoa, in Nigeria's delta region October 8, 2015. Tensions are building in the swampland of the Niger Delta as an amnesty that aimed to bring stability to Nigeria's volatile southern region is due to expire at the end of the year. While the region's towns and cities are mostly calm, local residents say kidnappings and armed robberies are on the increase in the mangrove swamps, where most oil wells are located. (Photo by Akintunde Akinleye/Reuters)

The Jet Propulsion Lab team's RoboSimian robot turns on a valve at a simulated disaster-response course during day one of the Defense Advanced Research Projects Agency (DARPA) Robotics Challenge finals in Pomona, California, June 5, 2015. (Photo by David McNew/Reuters)

Supporters of the presidential candidate Muhammadu Buhari and his All Progressive Congress hits another supporter with a motorbike during celebrations in Kano, Nigeria March 31, 2015. (Photo by Goran Tomasevic/Reuters)

A woman arrives at the Shinto Meiji Shrine to pray on the first day of the new year in Tokyo, Japan, January 1, 2016. (Photo by Thomas Peter/Reuters)

Owners and their dogs take part in “HK Doggie Dash 2018”, an event held to raise money for for abandoned and surrendered dogs in Hong Kong on April 15, 2018. Dozens of pugs and dachshunds compensated for their modest speed with peppy spirits at Hong Kong’s inaugural “doggie dash” on April 15 that raised funds and awareness for the city’s abandoned and rescued dogs. (Photo by Isaac Lawrence/AFP Photo)