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 man is silhouetted in front of the Allianz-Arena as he walks his dogs at sunrise in Munich, southern Germany, Friday, April 10, 2015. (Photo by Peter Kneffel/AP Photo/DPA)

Devotees of the Chinese Jui Tui shrine are seen with spikes piercing their cheeks during a procession celebrating the annual vegetarian festival in Phuket, Thailand in this October 19, 2015 combination photo. The festival, featuring face-piercing, sacrifice, spirit mediums and strict vegetarianism celebrates the local Chinese community's belief that abstinence from meat and various stimulants during the ninth lunar month of the Chinese calendar will help them obtain good health and peace of mind. (Photo by Jorge Silva/Reuters)

A young woman holds her smartphone at Red Square with the Kremlin's Spasskaya Tower, right, and St. Basil Cathedral, center, in the background in Moscow, Russia, Monday, July 25, 2016. (Photo by Pavel Golovkin/AP Photo)

A man dressed in leaves and animals of the forest, the Redeemer on his shoulder, holding the Olympic torch and wearing Olympic rings glasses walks along Copacabana Beach, Rio de Janeiro, Brazil, 31 July 2016. The 2016 Olympic Games start on 05 August. (Photo by Barbara Walton/EPA)

One of the poor families collecting firewood from the street and the burn to feel some warmth in Aleppo, Syria on August 19, 2016. (Photo by Basem Ayoubi/Imageslive/ZUMA Press/Splash News)

Children dressed up as Hindu Lord Krishna pose during Janmashtami festival celebrations marking the birth anniversary of Krishna in Agartala, India August 24, 2016. (Photo by Jayanta Dey/Reuters)

In this photo taken late Thursday, May 7, 2015, a prison guard, left, and seated inmates cast shadows on a wall while waiting for the beginning of a rock concert by Romanian band Pro Musica, inside the Popa Sapca jail in Timisoara, western Romania. (Photo by Adi Piclisan/AP Photo)