The attack on two U.S. Immigration and Customs Enforcement (ICE) agents in Mexico on Feb. 15 that left one of the agents dead was a targeted hit sanctioned by the top ranks of the Los Zetas cartel, according to investigators' working theory behind the attack, STRATFOR sources with knowledge of the investigation reported. Well-placed U.S. federal security sources indicate that the agents may in fact have been targeted because of their status as U.S. federal agents, which could have implications for future U.S. involvement in counternarcotics operations in Mexico. Evidence available at present now suggests an incident that began as a random encounter, rather than a pre-planned ambush, but evolved into a targeted hit once the agents were identified as U.S. federal law enforcement. It was originally thought that the men were targeted because they were driving in a high-profile, fully armored Chevrolet Suburban SUV, a valuable commodity among cartel members. While the attackers' original intent may have been carjacking, according to STRATFOR sources, the two agents made an unscheduled stop for lunch at a fast-food restaurant along the route before the incident, possibly allowing scouts to identify them as U.S. law enforcement. This could have given individuals affiliated with Los Zetas the opportunity to prepare what sources have called a "rolling road block" — an impromptu, non-permanent roadblock — along Highway 57. According to sources, the agents' vehicle had diplomatic license plates, which would have exposed them as federal law enforcement personnel, a detail the attackers are not likely to have missed. (There is reportedly a specific two-letter code issued on license plates to federal agents inside Mexico.) According to STRATFOR sources, the agents believed the Mexican military was operating the roadblock. As the surviving ICE agent begins to provide more information, the tactical details and motive for the attack will become clearer. The main outstanding questions are why the gunmen did not kill both men whom they knew were U.S. agents to avoid leaving witnesses, a common Zeta tactic, and why they did not destroy the car to conceal evidence. Given that this is not Los Zetas' typical modus operandi, not killing the second agent and not destroying the car may not have been an oversight, but a conscious decision. If so, that leads STRATFOR to question why Los Zetas (or others) would want to attract attention from U.S. law enforcement by carrying out an overt attack on U.S. agents that would seem to warrant a U.S. response.