Attacking worshipers in their places of worship is haram — utterly forbidden. Those that do this are devils, committing mischief in the land. It is hirabah — banditry, piracy — waging war against God.
“Permission to fight has been given to those who are being fought, because they were wronged. And indeed, God is competent to give them victory. Those who have been evicted from their homes without right, only because they say, “Our Lord is God.” And were it not that God checks the people, some by means of others, there would have been demolished monasteries, churches, synagogues, and mosques in which the name of God is much mentioned. And God will surely support those who support Him. Indeed, God is Powerful and Exalted in Might.” — Quran 22:39-40
The way of God is to protect monasteries, churches, synagogues and mosques — and the worshipers within — from destruction at the hands of brigands and aggressors. Any other way is the way of devils. By their fruit you shall know them.