Now Nkurunziza's rule could be extended again — on Thursday, Burundi held a referendum on constitutional reforms that could allow Nkurunziza to stay in power until 2034 — and Burundians are bracing for another potential wave of unrest.
Nkurunziza has led Burundi since 2005, when he was sworn in after the end of the country's brutal 12-year civil war. That year, he won a parliamentary vote that was mandated as part of the peace agreement; in 2010, the opposition boycotted the elections, and Nkurunziza, who ran uncontested, won with more than 91 percent of the vote.
Then, in 2015, the former teacher and guerrilla leader announced that despite the constitution's two-term limit, he qualified for a third because his first term in office had not been determined by a popular vote. Burundi's top court validated his move, but international partners — including the United States — called it unconstitutional.
The country plunged into chaos. Protests turned into violent clashes between security forces and civilians, and police officers responded with tremendous force. In the months that followed, the United Nations high commissioner for human rights announced that Burundian security forces were gang-raping women and that his office had identified mass graves.
More violence broke out ahead of the vote last Friday, when unidentified men wielding guns and machetes stormed a village near the border of the Democratic Republic of Congo and killed 26 people. Nearly half those killed were children. The government called the attackers "terrorists," and it's unclear whether the incident was linked to the referendum.
Given that history, observers worry that there is only one safe choice for voters on Thursdays — and Nkurunziza himself has implied as much. “Whoever opposes this election will meet God’s power,” he warned on the campaign trail in early May. Those who advise voters to boycott the polls on Thursday could serve up to three years in jail, according to a recent presidential decree. Many dissenters are no longer living in the country.
"What he’s done since  shows he wasn't merely trying to fulfill his legal right, but he was just finding an excuse to stay in power," said Joe Siegle, the director of research at the Africa Center for Strategic Studies.
If approved, the constitutional changes would lengthen presidential terms from five years to seven and allow Nkurunziza to run two more times after his current term expires in 2020. Nkurunziza has denied that he is angling to become president for life and, before being elected for his third term, reportedly told other East African leaders that he would not seek a fourth.
Despite the controversy and violence, the president does still have support, particularly from those who fear that bringing someone new into power could plunge Burundi back into war. Others see some of his initiatives, including free mother-and-child healthcare, as crucial.
Toying with presidential term limits has become something of a trend across Africa, where multiple leaders have either ignored term limits, refused to implement them or found their way around them. But a recent study released by Siegle's office found that term limits in Africa are also linked to stability.
Siegle said the current situation in Burundi is "a stereotypical case" of avoidable, internally driven conflict.
Most journalists have been denied access to the country ahead of the vote, and both the BBC and Voice of America were banned for allegedly violating broadcast regulations.