"It is totally intolerable and sends clear message to each media person that his or her life in risk because of his or her media activity," Omar Faruk Osman, NUSOJ secretary-general, said in a statement.
"We have been appealing to political groups to end killing of media people, but no group listens," Osman said.
Ga'far Mohamed Kukay, the stations acting director, said the killing shocked staff and more than a dozen remained inside the station's headquarters, fearing to go to their homes.
"It was very shocking act of revolting savagery," said Kukay.
He said the station had halted its normal programming after the killing so staff could mourn their colleague.
The Committee to Protect Journalists, based in New York, condemned the attack and urged the government in a statement to "ensure that all Radio Shabelle staff can return to their respective homes safely".
Radio Shabelle, one of the country's largest radio stations, resumed broadcasts on October 2 after a 15-day closure because government soldiers had threatened to pound it with missiles and machine gun rounds.
During Gedi's funeral, authorities in the northern area of Puntland arrested three reporters from Radio Garowe after the station aired a story criticizing the national security service, NUSOJ said.
Journalists in Somalia - which has had no central government since Mohamed Siad Barre was overthrown in 1991 - routinely face death, arbitrary imprisonment and harassment.
The danger has intensified since the Somalia's government backed by Ethiopian military forces, expelled Union of Islamic Courts fighters from Mogadishu last year.
Journalists have faced attacks from both the government and armed fighters angered by controversial reports published by Somalia's press.
In September, the government rounded up 18 of the broadcaster's journalists.