Violence against priests in Mexico

In this NEWS.VA article, Pope Francis calls the recent murder of Mexican priest, Rev. Gregorio López Gorostieta, "unjustifiable violence" and "urges all priests, and other missionaries, to continue in their mission despite the difficulties encountered, following the example of Jesus, the Good Shepherd."  Although a motive has not yet been determined, this article from Catholic Online suggests that it was related to a homily in which the priest spoke out against the drug cartel.  Additionally, it indicates that this was the third such incident in recent times.