A leading lawyer and adviser to Aung San Suu Kyi's National League for Democracy (NLD) party has been shot dead at Yangon airport in Myanmar.
Ko Ni was shot in the head at point blank range on Sunday after arriving at the airport. He was holding a child, reportedly his grandson, at the time. A taxi driver was also shot dead.
A suspect has been detained but there are no details on the motive.
Ko Ni was one of few prominent Muslims in a country dominated by Buddhists.
It is not clear if that was a factor in his death. Political killings are extremely rare in Myanmar, also called Burma.
His daughter, Yin Nwe Khine, told Reuters he was "often threatened" because he had spoken out against the continuing influence of the military on politics.
"We were warned to be careful, but my father didn't accept that easily. He always did what he thought was right.
"A lot of people hate us because we have different religious beliefs, so I think that might be why it happened to him, but I don't know the reason."
A vocal Muslim in a Buddhist country - by Jonah Fisher, BBC News, Yangon
A still picture taken by the taxi rank of Yangon's airport captured the moment of assassination.
A man wearing a pink shirt, shorts and flip flops points a pistol to the back of the head of Ko Ni, who is holding a small child.
Moments later Myanmar's most prominent Muslim lawyer was dead and shortly afterwards a taxi driver, too, who had chased the attacker.
Pictures posted on social media showed the police as they caught the attacker, his head and legs smeared in blood. He's been named as Kyi Lin, a 53-year-old from Mandalay.
A student activist dating back to the uprising of 1988, Ko Ni was a political prisoner and then, once released, a senior lawyer and adviser to Aung San Suu Kyi's political party. An expert on constitutional law, he worked on the NLD's plans to amend Myanmar's military drafted charter.
Last year he helped found the Myanmar Muslim Lawyers' Association and spoke of the need to stand up for the rights of Muslim citizens. That may have made him some powerful enemies.
Kyee Myint, a former chairman of the Myanmar Lawyer Network, said Ko Ni had been "a beloved friend".
"He is the face of the democracy in our country and this is a big loss for us," the Associated Press quoted him as saying.
Anti-Muslim feeling is high in Myanmar, and there is significant public support for a military operation in Rakhine state, which is home to thousands of Rohingya Muslims.
Rohingya are denied citizenship and are considered illegal immigrants by the government.
Rights group Amnesty International said Ko Ni's death would "send shock waves across the human rights community in the country and beyond".
"The authorities must send a clear message that such violence will not be tolerated and will not go unpunished," said Josef Benedict, Amnesty's regional deputy campaigns director.
A spokesman for Myanmar's President Htin Kyaw said police were questioning the man detained "to find out why he killed him, and who is behind it or paid him to do it".