U.S. and Mexican investigators are looking into the killing of an American Immigration and Customs Enforcement agent and the wounding of another in northern Mexico this week by suspected drug traffickers. The incident has rank-and-file agents on both sides of the border accusing ICE of failing to protect them.

Special Agent Jaime Zapata was one of 30 ICE agents posted in Mexico. On Tuesday, he and Special Agent Victor Avila were driving a big blue armored Chevy Suburban with diplomatic plates from San Luis Potosi to Mexico City.

Rep. Michael McCaul (R-TX), who was briefed by ICE, says the pair had stopped for lunch. When they left the restaurant, the gunmen followed them and ran them off the road. When the agents identified themselves, the cartel members opened fire. Mexico forbids U.S. law enforcement from carrying weapons on its territory.

The facts of the case raise questions: Why were federal agents driving a marked vehicle in an area with a known drug mafia presence that had a standing threat to kill U.S. officers?

“I would be asking questions regarding why they were in such a high-profile car?” says Fred Burton, a former deputy chief of diplomatic security for the State Department who is now with the global intelligence firm Stratfor. “What intelligence was known about that route 24 hours ahead of time? Where was the failure point?”

Retired ICE Deputy Director Alonzo Pena, who has experience in Mexico, said in an interview that all embassy personnel drive those armored sport utility vehicles, and that the safety of agents is paramount. An ICE official, speaking on background, added there were no embassy travel restrictions on the section of highway where the agents were attacked, and there were precautions taken to keep them out of cartel country.

But this and another incident have left ICE agents shaken, and wondering if the law enforcement agency they work for is adequately protecting them in an increasingly violent criminal environment.

“We definitely feel that the incident in Mexico is a clear indication that there is a significant problem, that our officers and our agents are outgunned, that we’re not handling this situation on either side of the border appropriately,” says Chris Crane, an active-duty ICE agent and president of the National ICE Council, which represents 7,000 agents and employees.

The Mexico shooting closely follows an incident that happened in San Antonio on Jan. 13. According to the police report obtained by NPR, masked gunmen burst into an ICE agent’s apartment. They held his fiancee at gunpoint, molested her and when they realized the agent wasn’t there, left. The agent’s job was to interview illegal immigrants in jail and decide if they could be deported. The local ICE office declined to discuss the incident.

ICE moved the agent and his fiancee to another residence and sent out an

e-mail warning to federal immigration agents in the Laredo-San Antonio region, but only after pressure from the union, Crane says.

“I was outraged,” he says. “We had to get in and call headquarters that night and say, ‘Hey, this guy needs a protective detail, immediately. He needs to be relocated, immediately.’ I mean, ICE doesn’t even have a policy in place to address situations like this.”

ICE agents complained for some time —- because of the sensitivity of immigration policy —- that the agency treats them as pseudo-cops. For instance, ICE agents contend they are not allowed to have Tasers and the policies on use of handcuffs, batons and pepper spray are too restrictive.

Last June, local union presidents nationwide cast a vote of no confidence against ICE Director John Morton and Assistant Director Phyllis Coven.

Crane said the recent incidents in Mexico and San Antonio have deepened agents’ concern about the agency’s management and the growing climate of violence in which they work. Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.