Can we call anyone terrorist or not???

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Here in my country, there was a news that some anti terrorist agents suddenly attack someone in mosque. When anti terrorist agents attack him, he was in pray to God. The Mosque is very holy, that if we want to come inside we must open the shoes, or sandals, but they was attack him and kill him with complete outfit until the shoes inside the mosque. The problem was the victim not proven is he terrorist or not. We don't know he is terrorist in what case or when it was happen. We just know from news he was already dead with swollen in head, swollen at feet. His brother saw the body before buried him. So...What do you think about this case??