After his release from the prison, Chernozemski disappeared.
He moved to Italy, where he became an instructor for the Ustaše in a camp in Borgotaro.
He was then transferred to the Ustaše camp in Janka-Puszta, near Nagykanizsa in Hungary.
The main purpose of this camp was planning for the assassination of King Alexander I. Chernozemski was the instructor of the group of three Ustašas: Mijo Kralj, Zvonimir Pospišil, and Milan Rajic, who were preparing to assassinate the king.
On September 29, the four terrorists arrived in Paris, and on October 6 they split into two groups.
Chernozemski and Kralj moved to Marseille, where the king was expected to arrive on October 9, and Pospišil, and Milan Rajic, moved to Versailles where they planned a second attack in case of failure of the first one.
On 9 October 1934, Chernozemski carried out the murder,  after concluding that the other members of the group were unprepared psychologically.

As King Alexander's motorcade drove at a few miles per hour down a Marseille street in front of an adoring crowd, Chernozemski was able to emerge from the crowd, approach the king's car and leap onto its running board while concealing his Mauser C96 automatic pistol in a bouquet of flowers and chanting "Vive le roi" ("long live the king").
He shot Alexander repeatedly, hitting him twice, once in the abdomen and the other in the heart; King Alexander died within minutes.
The chauffeur—who tried to push Chernozemski off the car—and Alexander's companion in the car, French Foreign Minister Louis Barthou, were also shot.
Chernozemski killed the chauffeur, apparently unintentionally.
A police officer fired at Chernozemski but missed and fatally wounded Barthou.
The chauffeur died almost immediately, with his foot pressed on the brake of the car, providing the opportunity for a photographer outside the car to photograph most of the grisly affair.
Barthou might have survived, but did not, apparently because of inadequate medical attention.

After shooting a policeman who tried to seize him and inadvertently killing two bystanders, Chernozemski then futilely attempted to flee the scene but was struck by a slash from an escorting cavalryman's sabre, stunning him.
He then received a non-mortal bullet wound in the head from a nearby police officer, and was fatally beaten by the enraged crowd while the police stood back and watched.
Chernozemski was then brought in for interrogation.
Since the assassin was in critical condition, he was unable to say anything and succumbed to his injuries later that evening, 10 days before his 37th birthday.
The French police were unable to identify him; they could only register his tattoo, a skull with crossbones and a sign reading "V.M.R.O." (Bulgarian initials standing for Internal Macedonian Revolutionary Organization).
He was buried in an unmarked grave in the Marseille cemeteries with only two detectives and the gravediggers present at the funeral.
A Yugoslav journalist who saw the tattoo told the press it was the symbol of the IMRO.
In the night of October 10, the French police arrested in Paris the Ustaša terrorists Zvonimir Pospišil and Milan Raijc.
Five days later Mijo Kralj was arrested, who admitted everything.
As a result, an exhumation was organized and fingerprints were sent from Paris to Sofia and Belgrade.
On 17 October it was officially announced from Bulgarian police that the killer was Vlado Chernozemski.
After his release from the prison, Chernozemski disappeared. He moved to Italy, where he became an instructor for the Ustaše in a camp in Borgotaro. He was then transferred to the Ustaše camp in Janka-Puszta, near Nagykanizsa in Hungary. The main purpose of this camp was planning for the assassination of King Alexander I. Chernozemski was the instructor of the group of three Ustašas: Mijo Kralj, Zvonimir Pospišil, and Milan Rajic, who were preparing to assassinate the king. On September 29, the four terrorists arrived in Paris, and on October 6 they split into two groups. Chernozemski and Kralj moved to Marseille, where the king was expected to arrive on October 9, and Pospišil, and Milan Rajic, moved to Versailles where they planned a second attack in case of failure of the first one. On 9 October 1934, Chernozemski carried out the murder,  after concluding that the other members of the group were unprepared psychologically.
As King Alexander's motorcade drove at a few miles per hour down a Marseille street in front of an adoring crowd, Chernozemski was able to emerge from the crowd, approach the king's car and leap onto its running board while concealing his Mauser C96 automatic pistol in a bouquet of flowers and chanting "Vive le roi" ("long live the king"). He shot Alexander repeatedly, hitting him twice, once in the abdomen and the other in the heart; King Alexander died within minutes. The chauffeur—who tried to push Chernozemski off the car—and Alexander's companion in the car, French Foreign Minister Louis Barthou, were also shot. Chernozemski killed the chauffeur, apparently unintentionally. A police officer fired at Chernozemski but missed and fatally wounded Barthou. The chauffeur died almost immediately, with his foot pressed on the brake of the car, providing the opportunity for a photographer outside the car to photograph most of the grisly affair. Barthou might have survived, but did not, apparently because of inadequate medical attention.
After shooting a policeman who tried to seize him and inadvertently killing two bystanders, Chernozemski then futilely attempted to flee the scene but was struck by a slash from an escorting cavalryman's sabre, stunning him. He then received a non-mortal bullet wound in the head from a nearby police officer, and was fatally beaten by the enraged crowd while the police stood back and watched. Chernozemski was then brought in for interrogation. Since the assassin was in critical condition, he was unable to say anything and succumbed to his injuries later that evening, 10 days before his 37th birthday. The French police were unable to identify him; they could only register his tattoo, a skull with crossbones and a sign reading "V.M.R.O." (Bulgarian initials standing for Internal Macedonian Revolutionary Organization). He was buried in an unmarked grave in the Marseille cemeteries with only two detectives and the gravediggers present at the funeral. A Yugoslav journalist who saw the tattoo told the press it was the symbol of the IMRO. In the night of October 10, the French police arrested in Paris the Ustaša terrorists Zvonimir Pospišil and Milan Raijc. Five days later Mijo Kralj was arrested, who admitted everything. As a result, an exhumation was organized and fingerprints were sent from Paris to Sofia and Belgrade. On 17 October it was officially announced from Bulgarian police that the killer was Vlado Chernozemski.
Vlado Chernozemski