After Alexander I's father, King Milan I, abdicated the throne of Serbia, Alexander I was named king. The boy was to attain the throne at age 18, until which rule of Serbia would be undertaken by regents. However, Alexander I could not wait until he was officially an adult to attain full rule.
Alexander I proclaimed himself King of Serbia in 1893. Having been born in 1876, he was only 17 when he assumed the throne. This action was only the first example of Alexander I using his power to live how he wished, regardless of political consequences.
As a ruler, Alexander took full advantage of his title. He re-instated an older version of the then-current constitution, married a woman not of his parents' choosing, and sent his own mother away when she objected to his choice for consort. He dismissed government officials, chose his own representatives, and introduced a new constitution of his creation. In addition, he named an unpopular heir to the throne, a relation of his wife.
Unfortunately, this last action was Alexander I's downfall. In 1903, Alexander I and the Queen were cornered in the royal palace by military agents. The royal couple was murdered, and their bodies were tossed from the windows of the palace.
Shortly thereafter, Peter I assumed the throne. He had been living in exile and returned to Serbia when Alexander I was removed from power.