This is a question for a mufti, I dont like giving fatwas, but the Question is why is the Kafir killing him?I have a question sir, any Muslim killed by a kafir wouldn't be a martyr?
If it is simply because he is a Muslim, then given that he was a practicing good Muslim, then yes IA he would be a martyr.
But if the Muslim has broken a law, then No.
Nonetheless, point to be noted, is that we will never know 100% of the facts, so best not to indulge in anything of this sort.
Allah knows best.