As I said they killed them with the use of the blasphemy laws. A Muslim only needs to accuse the kafir.
For example if a Muslim accuses the kafir of burning the Qur'an then burn the person alive and there is no evidence that the qur'an was burned before or after the the victim was killed. This seems to be a common event now.
Sorry, but AFAIK there isn’t a single Muslim country where this is the law. It happens, and Muslims get away with it, but it’s extralegal.
Just as in the South during Jim Crow a white man could claim a black man attacked him or insulted a white woman and he’d get away with killing him. No evidence other than his own word needed. Under the formal law it was just as illegal for a white man to kill a black man as the reverse, but in practice there was a huge difference.