Zapata and Special Agent Victor Avila were driving back to Mexico City from a meeting with U.S. officials from Monterrey and stopped for sandwiches at a Subway shop in the city of San Luis Potosi, McCaul told CNN.  It is possible that the attackers began tracking them from that point, the congressman said.  Once on the highway, two vehicles carrying what are now believed to be members of the Zetas bracketed the agents' SUV, he said. The car in front of them braked, and the agents' vehicle made contact with it and went off the road, he said.  According to the reports McCaul has received, the agents put the car in park, which automatically unlocked the doors and which gave the assailants an opportunity to try to open the door. In the struggle to lock the doors, the SUV's window was partially rolled down.  Zapata and Avila told the 10-15 gunmen, "We're Americans, we're diplomats," according to McCaul. They responded by opening fire through the opening.  Investigators recovered 83 shell casings at the scene, he said.  "The question is whether they were rogue Zetas operating on their own, or if it was a sanctioned Zeta hit," McCaul said. New information, McCaul said, pointed to the latter.  It was unclear whether any of the information came from debriefings by Avila, who was recovering from his wounds after being discharged from the hospital Wednesday.  Earlier, Mexico's ambassador to the United States said his country will do everything it can to apprehend those who shot the two agents.  "Mexican law enforcement authorities and the Mexican government will do anything and everything in their power to find these individuals and swiftly bring them to justice," Ambassador Arturo Sarukhan said Wednesday.  His pledge came as the United States announced the formation of a joint task force to investigate Tuesday's shootings in Mexico.
New information regarding the killing of a U.S. immigration agent in Mexico points to it being a sanctioned hit by the Zetas drug cartel and not a rogue incident, said Rep. Michael McCaul, R-Texas,