Ilic (pronounced: Ilitch), a former Sarajevo school teacher, worked for a newspaper. He was an active member in the pro-Serb nationalist group Mlada Bosna (Young Bosnia) and a member of the Serbian secret society know as The Black Hand. Like many of his contemporary young group members, Ilic was sickly and probably consumptive.
Ilic was not one of the three men trained for the assassination by the Black Hand in Serbia, but had been on the fringes of terrorist societies for several years. When the Black Hand decided to assassinate the Heir-Apparent to the Austrian throne, Archduke Franz Ferdinand, Ilic was eager to join the plot. It was Ilic who recruited three additional local Sarajevans; Mehmedbasic, Cubrilovic, and Popovic, to give the assassin group a more grass-roots (and less Serbian inspired) appearance. Ilic gave the two high school students (Cubrilovic and Popovic) a one-day training course in their roles. Mehmedbasic had been involved in Black Hand plots before, though without particular success.
On the morning of June 28th, 1914, the six other assassins had assigned positions along the Appel Quay in Sarajevo. Ilic (who may have been unarmed) paced back and forth between the others, seeing that they were in position and giving words of encouragement. The first attempt -- a bomb thrown by Cabrinovic -- failed. Later that morning, another of the seven assassins -- Princip -- succeeded in killing Archduke Franz Ferdinand.
Ilic was picked up a few days later by Sarajevo police in a routine round-up of suspects. (Princip had stayed at his house.) Ilic lost his cool and told the police nearly everything about the plot in an attempt to mitigate a likely death penalty for his role. Up until Ilic's confession, the other assassins had maintained a successful code of silence. The tangled web had begun to unravel.
Danilo Ilic and the others were tried in October 1914. For his role in the assassination, Ilic was found guilty. While the other six were under 20 years old, and therefore not eligible for the death penalty, Ilic (23), was sentenced to death. He was executed by hanging on February 3rd, 1915, in a Sarajevo prison. He was the only one of the group of seven to be executed for their crime.