By Stefan J. Bos
Police investigators said 57-year-old Ognjanovic was killed late Saturday outside his Belgrade apartment building. A police statement added that Ognjanovic's son, who is 26, was wounded in his right arm.
Ognjanovic was part of the legal team that defended strongman Slobodan Milosevic at the United Nations war crimes tribunal in The Hague, Netherlands.
The former president of Serbia was detained in 2001 and held at the tribunal for genocide and other war crimes during the bloody break up of Yugoslavia in independent republics.
Milosevic was facing three indictments relating to atrocities carried out in independence-seeking Kosovo, another for crimes in Croatia, and the third
alleging genocide in Bosnia-Herzegovina between 1992 and 1995.
During the trial, Ognjanovic was at his side. He once spoke about helping to arrange a birthday visit for Milosevic family members. "He feels fine and alert. He is very happy to be with his grandson, daughter-in-law, and wife. They are together for three days for the full-time except Sunday," he told reporters at the time.
"They are very satisfied to be together without glass, without microphones so they can hug each other, kiss each other like very tight members of a family," Ognjanovic added.
But Milosevic never heard a verdict. He was found dead in his cell in 2006 before his trial could be completed.
In a statement, the head of the Bar Association in Belgrade which represents attorneys said the shooting of Milosevic lawyer Ognjanovic was an attack on all lawyers.
Bar head Viktor Gostiljac said he would in his words "exert maximum pressure on the competent state authorities to find the perpetrators of this crime."
Ognjanovic also served as a defense lawyer in several high-profile mafia cases in Serbia and Montenegro.
His killing underscores concerns about ongoing violence in the region as several prominent members of Serbian and Montenegrin organized crime networks have been killed in Belgrade in recent years.
Serbian police believe that the killings are part of a gang war over the illegal drugs market.
The violence comes at a sensitive time for Serbia which is seeking membership of the European Union.