Tanzania mourned at least 20 people killed in a stampede at a Pentecostal church on Saturday, plus another 20 killed by floods caused by torrential rains.

Boniface Mwamposa, the popular pastor of the church where the stampede occurred, was arrested while trying to flee the country after the deadly incident.

According to the authorities, Pastor Mwamposa of the Arise and Shine Ministry Tanzania, noted for referring to himself as “The Apostle,” packed thousands of people into a sports stadium in the town of Moshi near Mount Kilimanjaro on Saturday night. 

During the event, Mwamposa poured “blessed oil” on the ground and told his followers to walk on it, promising they would gain prosperity and be cured of disease. Twenty people were killed and 16 others injured when the crowd surged forward to do as Mwamposa suggested.

“It was horrible, people trampled on mercilessly, jostling each other with elbows,” an eyewitness told AFP. “It was like the preacher had thrown bundles of dollars about … and there were all these deaths!”

“The incident took place at night and there were many people, so there is a possibility that more casualties could emerge. We are still assessing the situation,” Moshi district commissioner Kippi Warioba said on Saturday.

Warioba said Mwamposa “tried to flee after this incident, but we arrested him in Dar es Salaam,” a port city from which Mwamposa might have hoped to leave the country. On Sunday the police broadcast a televised appeal to Mwamposa to hand himself in.

“He will be held accountable for causing this tragedy,” Warioba promised. Among other likely charges, Mwamposa has been accused of violating the terms of the permit he obtained for the sports stadium service and making inadequate preparations for such an enormous crowd.

“There has been a rise in the number of pastors who claim they can perform ‘miracle cures’ and eradicate poverty in Africa in recent years. Preachers who spread what they call the ‘prosperity gospel’ have been involved in financial scams and money laundering schemes, as well as other stampedes,” the Associated Press noted on Sunday.

Flash floods caused by torrential rains swept through 16 villages over the weekend and killed up to 20 people, leaving some 15,000 others homeless.

The floods destroyed a great deal of farmland, killed livestock, ruined buildings, wiped out roads, and disrupted other vital infrastructure.

Tanzanian President John Magufuli issued a statement mourning the dead from both stampede and flooding, declaring himself “very sorry for these deaths.”

Magufuli has been criticized by the U.S. government for deteriorating human rights in Tanzania, and there is some doubt he can be trusted to run a free and fair election in October. Sweden announced on Monday it will reduce foreign aid to Tanzania due to “negative democratic developments in the country.” 

The Tanzanian opposition on Monday asked for international support to “stand up for Tanzanians so they can choose their own future without fear and avoid being forced into a one-party state against their choosing.”