"Preliminary findings show a female who worked in the local government blew herself up with the help of another female, who . . . also worked at the local government," the ministry statement said. "The female bomber was disabled. She misused the opportunity and acted with enmity against the bosses and the people she worked with."
The Associated Press reported that visitors to the mayor's office typically must pass through a number of metal detectors, raising serious questions about how someone laden with explosives was able to gain such proximity to high-level officials.
Nicknamed "Engineer Yariisow," or "little engineer," as a nod to his engineering background, Osman was born in Somalia but fled to Britain after the country's central government collapsed and war broke out in 1991. He became a British citizen and found his passion in politics, eventually serving as a councilor for Britain's Labour Party.
He moved back to Somalia in 2009, leaving the safety of Britain behind in hopes he would help rebuild his native country. In Mogadishu, he went on to play various roles, including information minister.
Then, last year, President Mohamed Abdullahi dismissed Taabit Abdi Mohamed as Mogadishu's mayor and tapped Osman to replace him.
Osman's sudden, violent death has left the city reeling.
"The people of this city have lost a great man and a leader," Ibrahim Omar Mahadalle, Mogadishu's deputy regional administrator, told Voice of America Somali. "He led this city by example."
Ben Fender, the British ambassador to Somalia, tweeted a farewell to Osman, calling him a "kind and gentle colleague."
"Our hearts are so heavy today," he wrote. "We will join hands to finish the work you started, and the Somalia we build will be your greatest memorial."
Lawmaker Dahir Amin Jesow told Reuters that Osman was working to improve Mogadishu's security, and "was in the middle of constructing Mogadishu streets and roads."
Both civilians and officials face immense risk in Mogadishu, where attacks are carried out on a regular basis. Al-Shabab militants have long sought to overthrow the government and rule under an hard-line interpretation of sharia law.
The United States and regional partners in Africa provide a tremendous amount of military support to Somalia, but al-Shabab continues to carry out attacks across the country. In July, militants attacked a hotel in the coastal city of Kismayo, killing Hodan Nalayeh, a prominent Somali-Canadian journalist who had recently returned to Somalia to tell uplifting stories. She was one of at least 26 people killed in that attack.
Osman's body was flown back to Somalia this week for burial. And on Friday, the president renamed a stadium in the capital for him, to honor his legacy, AfricaNews reported.
"Today we name this stadium after Abdirahman Omar Osman," Abdullahi said at an official ceremony. "He deserves more than this."