Mount of Olives Church

The Mount of Olives Church had been participating in a ritual for four years, in which a butane lamp was lit with all the doors and windows killed. During these services, the lamp caused the room to fill up with toxic fumes, but when church members felt the effects of the poison, they were told it was the manifestation of Christ.

This ritual happened for the last time in December of 1991. After the pastor's daughter fainted during the service, the pastor encouraged the congregation to keep worshipping, saying, "Let Christ come and be among us, don't be afraid."  This energized the congregation in their worship and made them unconcerned as more and more members began vomiting and fainting throughout the night.

When relatives noticed their loved ones had not returned by the following day, they went to the church to investigate and found a building full of dead bodies. In the end, 30 people died, including 13 children.

Other info:

• Members believed that feelings of sickness or lightheadedness were evidence that Christ was among them (source)