MOGADISHU, Somalia — Gunmen stormed a hotel in Somalia’s seaside capital Saturday, taking guests hostage and “shooting at everyone they could see,” before security forces pursued the grenade-throwing assailants to the top floor and ended the hours-long assault, police and witnesses said. At least 14 people were killed. Islamic extremist group al-Shabab claimed responsibility for the latest in a series of hotel attacks in Mogadishu, one that began with a powerful explosion at the entry gate. “We have finally ended the siege.