KO NI was shot in the head at close range in broad daylight. He was waiting for a taxi outside Yangon’s bustling international airport, holding his three-year-old grandson in his arms. A prominent lawyer and adviser to the ruling National League for Democracy (NLD) party, he had just returned from Indonesia, where he had been part of a delegation studying democracy and conflict resolution.

Mr Ko Ni was also a Muslim and a prominent defender of religious minorities in a country seething with anti-Muslim sentiment. The climate has worsened since attacks on Burmese border guards last October that have been blamed on the Rohingya, a persecuted Muslim minority group. Since then the Burmese army has taken a scorched-earth approach in northern Rakhine state, home to the largest concentration of Rohingya. Human-rights groups and international monitors have accused the army of torching villages and raping and murdering many of their inhabitants. Mr Ko Ni, who was not himself Rohingya, spoke against the law that long ago stripped them of citizenship. That was daring: most people close to the government see the Rohingya as interlopers from Bangladesh, with no right to stay in Myanmar.

Unsurprisingly, Mr Ko Ni had received death threats from Buddhist extremists. One Muslim activist who preferred to remain anonymous said: “People who speak against the nationalists…people who speak the truth about the situation in Rakhine state…are not secure.”

Whether Mr Ko Ni’s killer targeted him because of his religion and as a prominent advocate of tolerance remains unclear. Police arrested a 54-year-old named Kyi Lin shortly after the killings. (Taxi drivers at the airport had chased the fleeing gunman; he shot one of them dead before being overpowered by others.) Little is known about him. Initially he claimed to come from Mandalay, the country’s second city, but police later said that was untrue.

The Irrawaddy, an independent news website, reported that Mr Kyi Lin told police he had been hired by a man named Myint Swe, who had promised to reward him with a car. Both men have reportedly dabbled in illegal antiquities-dealing, but no clear motive has emerged for the murder. Police later said they had arrested Mr Myint Swe near the border with Thailand.

But that makes Myanmar no less anxious. Some NLD members suspect Mr Ko Ni was chosen for his religion—not out of bigotry, but to undermine the government through religious discord. Nyan Win, an NLD executive-committee member, said in a televised interview that he feared further assassinations. Some see a military link: Mr Ko Ni was a constitutional expert, and had advised the government on reforms to the charter, imposed on the country in 2008 after a sham referendum, that gives vast and unaccountable power to the army. A press release from the president’s office after the murder claimed its intent was to “destabilise the state”.

If so, it has failed—for now. After Mr Ko Ni’s murder, friends and relatives gathered near his home in Yangon’s colonial district. “We are very angry”, said one Muslim NLD member, “but we will control our anger.” Ko Lay, a 43-year-old sailor who lives nearby, said Mr Ko Ni “did so much good for the country, but we cannot always know if people love him or hate him.”