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)

Festival goers run toward the main stage to catch the beginning of Kendrick Lamar's set during the first weekend of Coachella 2012, on April 13, 2012. (AP Photo/Chris Pizzello)

Race goers are pictured during the Investec Ladies Day at Epsom Downs Racecourse on June 2, 2017 in Epsom, England. (Photo by News Group Newspapers Ltd)

Festival goers having fun at the Balaton Sound music festival in Zamardi next to the Lake of Balaton, 110 km (68 miles) west of Budapest, July 8, 2017. (Photo by Sandor Csudai)

Festival-goers take photo inside of Spectra, a seven-story spiral walkway up to a viewing deck, at the Coachella Valley Music and Arts Festival in Indio, California, on April 17, 2022. (Photo by Valerie Macon/AFP Photo)

General view of festival goers at the main stage on Day 3 of Download festival at Donnington Park on June 12, 2022 in Donnington, England. (Photo by Chris Bethell/The Guardian)

Festival goers attend the 2023 Coachella Valley Music and Arts Festival on April 14, 2023 in Indio, California. (Photo by Matt Winkelmeyer/Getty Images for Coachella)

Two drunk race-goers make their way home after the last race of the third day of the Royal Ascot horse racing week June 19, 2003 in Ascot, England. (Photo by Scott Barbour/Getty Images)