Mohibullah, the head of the Arakan Rohingya Society for Peace and Human Rights (ARSPH) who was known by one name, was killed by unknown gunmen in the Kutupalong refugee camp, in the southeastern Bangladeshi district of Cox’s Bazar, on Wednesday night.

Police made three arrests on Friday in connection with the killing, but have so far provided no further details.

Over 700,000 Rohingya fled their home country of Myanmar to Bangladesh following a brutal crackdown by the military in 2017.

What has Bangladesh promised?

“The government will take stern action against those who were involved in the killing. No one will be spared,” Foreign Minister A.K. Abdul Momen said in his first comment since the killing.

Momen added that “vested” interests were responsible for the killing as Mohibullah had wanted to return to Myanmar. “The killers will certainly be brought to justice. None will be spared,” he said.

Are there any suspects?

The three people arrested on Friday are believed to have links to an armed insurgent group among Rohingya refugees.

They are currently being interrogated, said Naimul Huq, a police official in Cox’s Bazar.

In an unverified video circulated on social media, Mohibullah’s brother, Habib Ullah, who said he witnessed the shooting, blamed the Arakan Rohingya Salvation Army (ARSA), an armed group active in the camps.

ARSA said in a post on Twitter on Friday that it was “shocked and saddened” by the killing and decried “finger-pointing with baseless and hearsay accusations.”

Who was Mohibullah?

Mohibullah was known as a moderate who advocated for the Rohingya to return to Myanmar with rights they were denied during decades of persecution.

He founded the Arakan Rohingya Society for Peace and Human Rights in a bid to document atrocities against Rohingya in their native Myanmar and give them a voice in international talks about their future.

But his high profile made him a target of hard-liners, and he received death threats.

The killing has ignited grief and anger in the camps that make up the world’s largest refugee settlement.