The young girls's father and brother were murdered by the terrorist group. The father would not renounce his faith.
You can read more about Boku Haram from the sources below:
- Vox has an excellent review of the organization called "The crisis in Nigeria, in 11 maps and charts."
- Vox has another good story called "Vox.com offers a few basic facts about Boko Haram tactics."
- The BBC has a great background story called "Who are Nigeria's Boko Haram Islamists?
And here, from the BBC story, is Boku Haram explained in 60 seconds.