But going down in the sea or the mountains of Vietnam doesn’t seem very productive from a terrorism point of view.
And no one has claimed responsibility.
5.56mm
Some unknown Uigher group did claim responsibility, but I’d suspect it’s probably Asian-European Muslims (that is, Russians such as Chechens or Dagestanis) who were either showing support for their Asian brethren or - more likely - had a work accident while transporting a terrorist weapon to a European target.