Minutes before he died, aged 32, in a fire, the activist Luc Nkulula, trapped by the flames in his wooden house, was passing his life’s work out through the barred window. He died as he had lived: thinking first of Lucha, the movement he and other fearless young Congolese had built, enduring arrests, beatings and repression in order to further their ideals of democratic change and creating a future for the youth of the Democratic Republic of the Congo.

“Congo is great; it requires greatness of spirit,” was Nkulula’s motto, apparently borrowed from Patrice Lumumba, the DRC’s first democratically elected leader, who was assassinated in a coup allegedly sponsored by Belgium and the CIA.

Nkululu joined Lucha, or Lutte pour le Changement (Struggle for Change) in 2012, not long after the movement was founded in the eastern city of Goma. When the Congolese president Joseph Kabila met Lucha activists in summer 2016 after years of repression, it was Nkulula who did most of the talking. He asked Kabila, then at the end of his constitutional mandate, to leave power.

Few have believed Kabila’s repeated assurances since then that he is about to step down. Much of the violence that has forced 4.5 million people to flee their homes seems to be part of Kabila’s plan to cling on at the DRC’s helm. After the era of plunder under King Leopold II of Belgium that ended in 1909, and then half a century more of colonialism, this huge and diverse country had Lumumba as prime minister for less than three months in 1960 before he was killed. Since then, Mobutu Sese Seko and the Kabilas have successively been in charge.

Nkulula was notoriously straight-talking, but telling Kabila to get out took a rare kind of bravery. According to other Lucha members, the president was asking the group to give him more time to organise elections. After the meeting, he released their comrades from prison.

The idea that Kabila would plead with young, seemingly powerless people for a reprieve is testament to the respect Lucha had built up. Six years after its founding, the organisation now has around 3,000-4,000 members, mostly aged under 25, and though their ability to mobilise the masses is modest, they have established a considerable presence. Lucha refused to grant the president’s request for more time, and continued their protests demanding his resignation.

I met Nkulula a few months after Kabila did, in a quiet garden cafe in Goma, but we had to move location to escape intelligence agents, who were always trailing Lucha members. Most people in the DRC are careful what they say. Nkulula spoke his mind, and was open in criticising Kabila.

He was born in Lubumbashi, in the south-east of what was then Zaire, and grew up between there and Goma; his mother, Nunu Kabuo Kakule, worked for the state air transport company, and his father, Emile Mwamba wa Nkulula, was a doctor. Luc studied law at Goma University, and did legal consultancies for international organisations after graduating. After joining Lucha he helped shape it into a movement that did not just talk, but took action.

A few days after I met him, he was at a Lucha meeting in a school courtyard in Goma, sitting with his comrades on lumps of lava from the volcano that looms, and sometimes explodes, over the city. As children played basketball behind them, the group discussed logistics for an upcoming “ville morte” demonstration. Was two days of a stay-at-home protest financially possible for the hard-up population? Should protesters sing a well-known protest song, risking arrest if the police heard?

Nkulula was the first in Lucha to be arrested, in 2012, and he spent weeks in the cells and received many death threats. His nickname was H2O, because of his vital role in the movement. “Does that mean we’ve lost hope to continue the battle? Not at all, because the water Luc gave us is the same water we’ll use to carry on the struggle,” said his friend Juvin Kombi.

The Lucha leadership thinks Nkulula was assassinated. The same public prosecutor who continually brought charges against Nkulula and his friends was initially given the task of investigating the matter. But after Lucha complained, the UN peacekeeping mission has also launched an inquiry.

In the DRC, the dead are often counted by the million. Ten million killed under Leopold; four million in the war that began after Mobutu’s overthrow in 1997; right now nearly half a million children in one wartorn province, Kasai, are on the verge of dying of malnutrition. But Nkulula’s death, like Lumumba’s, stands out because of the promise he represented of changing politics in the DRC.

“I’m not scared of dying, I’m scared of dying without having fought for my dignity and that of my people,” he once said.

His mother died in 2010. He is survived by his father, Emile, and his sister, Amen.

• Luc Nkulula Wamwamba, political activist, born 18 October 1985; died 10 June 2018