Islamic extremists used knives to kill 15 Christians in the northern Nigerian village of Musari. The Friday attack happened in a town considered a stronghold of the al-Qaeda related group Boko Haram although the government has released few details.

A school teacher in Musari told the Associated Press the terrorists gathered all the Christians into one room before committing the massacre.

“The victims were selected because they were all Christians,” a relief worker told the press. “Some of whom had moved into the neighborhood from other parts of the city hit by Boko Haram attacks.”

It’s been a deadly week for Christians in Nigeria as the Musari deaths bring the weekly death total to 28. Boko Haram has stated a goal of eliminating all Christians and imposing Sharia Law.