BROWNSVILLE, Texas -- Homeland Security Secretary Janet Napolitano and U.S. Attorney General Eric Holder were among those expected to attend Tuesday's funeral for a federal agent killed in Mexico during what U.S. officials described as a roadside ambush carried out by drug cartel gunmen

Immigrations and Customs Enforcement Special Agent Jaime Zapata was to be buried in his hometown on the U.S.-Mexico border one week after the 32-year-old was shot and killed while sitting in his car. His death brought together nearly 1,000 mourners Monday night at a prayer service, led by a South Texas bishop who said the entire country grieved with the family.

Napolitano, Holder and ICE Director John Morton were all expected to speak at the funeral service Tuesday morning. Holder and Napolitano last week announced the creation of a joint task force to find Zapata's killers.

Fellow ICE agent Victor Avila was in the car with Zapata but survived the attack after being shot twice in the leg.

Zapata and Avila were attacked when a group of Zeta drug cartel members in two vehicles forced Zapata's sport utility vehicle off a highway, U.S. Rep. Michael McCaul has said. Avila was released from a Houston hospital last week.

San Luis Potosi borders two northern Mexican states where the Zetas and the rival Gulf Cartel have waged bloody battles over territory. Zapata and Avila were temporarily detailed to the ICE attache office in Mexico City and were driving from the northern city of Monterrey to the Mexican capital at the time of the attack.