Assassination
The general impression was that, as much as the senate was packed with men devoted to the royal couple and the government obtained a large majority at the general elections, King Alexander would not hesitate any longer to proclaim Queen Draga's brother as the heir presumptive to the throne. In spite of this, it had been agreed with the Serbian Government that Prince Mirko of Montenegro, who was married to Natalija Konstantinovic, the granddaughter of Princess Anka Obrenovic, an aunt of King Milan, would be proclaimed heir-presumptive in the event that the marriage of King Alexander and Queen Draga was childless.
Apparently to prevent Queen Draga's brother being named heir-presumptive, but in reality to replace Alexander Obrenović with Peter Karađorđević, a conspiracy was organized by a group of Army officers headed by Captain Dragutin Dimitrijević also known as "Apis", who was in the pay of the Russians, as well as the leader of the Black Hand secret society which would assassinate Archduke Franz Ferdinand in 1914. Several politicians were also part of the conspiracy, and allegedly included former Prime Minister, Nikola Pašić. The royal couple's palace was invaded and they hid in a cupboard in the Queen's bedroom. There is another possibility, used in a Serbian history TV series "The End of the Obrenović Dynasty", in which the royal couple was hidden in a secret panic room hidden behind the mirror in a common bedroom. The room contained an entrance to a secret passage leading out of the palace, but the entrance was inaccessible due to the placement of the queen's wardrobe over it after the wedding.
The conspirators searched the palace and eventually discovered the royal couple and murdered them in the early morning of June 11, 1903. King Alexander and Queen Draga were shot and their bodies mutilated and disemboweled and, according to eyewitness accounts, thrown from a second floor window of the palace onto piles of garden manure. The King was only 26 years old at the time of his death. King Alexander and Queen Draga were buried in the crypt of St. Mark's Church, Belgrade.
Read more about this topic: Alexander I Of Serbia