Here. It comes down to this,
"Non-indigenes are openly denied the right to compete for government jobs and academic scholarships. Members of the largely Muslim Hausa ethnic group are classified as non-indigenes in Jos and surrounding communities, though many have lived there for several generations."
There are some eye-witness accounts to the massacres at the bottom of the article. Violence in Jos will continue to break out sporadically until the wholly artificial indigene-settler distinction is removed in practice by the state government.