• Kim Jong Un’s elder half-brother was assassinated at a Malaysian airport on February 13, 2017.
  • One year later, many questions surrounding Kim Jong Nam’s death remain unanswered.

It’s been one year since the half-brother of North Korean leader Kim Jong Un was assassinated at a Malaysian airport — but the much of the case remains a mystery.

Kim Jong Nam was killed after two women rubbed a lethal nerve agent called VX on his face at Kuala Lumpur International Airport on February 13, 2017.

Both women, who have been charged with murder, have consistently maintained their innocence, claiming that they thought they were participating in a prank for a TV show. Four men have been charged as well, but are still on the run.

The murder trial started last October and is scheduled to finish on March 22, 2018.

Here’s what we know about the assassination — and what we still don’t.