Federal Police agents present Jesus Enrique Aguilar, alias &quot;El Mamito&quot;, center, to the media in Mexico City, Monday July 4, 2011. Police believe Aguilar is connected with the killing of a U.S. Immigration and Customs Enforcement agent. Aguilar is a former member of the Mexican Army and allegedly a co-founder of the Zetas drug cartel, according to authorities. (AP Photo/Alexandre Meneghini)