The New York Times, 2/24/2011
The Mexican Army said Wednesday that it had detained a man suspected in the shooting death of a United States Immigration and Customs Enforcement agent and the wounding of another on a Mexican highway last week. The detained man was identified as Julián Zapata Espinosa, known as El Piolín, a leader of the Zetas gang in San Luis Potosí. The agents were ambushed and fired on as they drove from San Luis Potosí State to Mexico City. The motive was not clear but speculation has focused on a possible carjacking.
Mexico Institute 