At least six armed individuals entered the shelter in the early morning hours of May 6 and stole some of the migrants' meager possessions, including cash, cellphones and ID cards.
In April scores have died in a series of attacks and assassinations in Mexico, the Philippines and Nigeria. Catholics at prayer during Mass have been targeted in a number of attacks.
The April 7 letter, addressed to people in Mexico and the United States and the presidents of both countries, echoed sentiments of U.S. border bishops by saying the frontier between the two countries "is not a war zone".