In the Monday attack, the gunmen ordered Muslim passengers to come out of the bus and separate themselves from the Christians.
There were more than 100 passengers on board.
The Muslim passengers refused.
They gave the Christian women their hijabs and helped others hide behind bags in the bus, passenger Abdiqafar Teno told CNN.
“They told them, ‘If you want to kill us, then kill us. There are no Christians here,” he said.
A Christian man who tried to run away was captured and shot dead, Teno said. The driver of a truck, which was trailing the bus, was also killed.
The gunmen left, but warned they would return.