Indictments against the three are still sealed, but another court document identifies them as Ruben Dario Venegas Rivera, alias “El Catracho”; Jose Ismael Nava Villagran, alias “Cacho”; and Francisco Carbajal Flores, who has at least four aliases.

Those three join Julian “Piolín” Zapata Espinoza as suspects indicted by a U.S. federal grand jury in connection with the Zapata murder, the document indicates.

The case also involves the attempted murder of Victor Avila, also a special agent with Immigration and Customs Enforcement. Zapata and Avila were working together in Mexico when they were attacked.

Only the indictment against Zapata Espinoza, who has been extradited from Mexico to the United States, has been unsealed.

On Dec. 21, Mexican authorities handed Zapata Espinoza to the FBI at the international airport in Veracruz, Mexico.

The next day, he pleaded not guilty in federal court in Washington to a four-count indictment that charged him with murder, attempted murder, attempted murder of an internationally protected person, and using, carrying, brandishing and discharging a firearm during a crime of violence, causing death. Each count also carries the charge of aiding and abetting and causing an act to be done.

The indictments against Venegas Rivera, Nava Villagran and Carbajal Flores were still sealed as of Tuesday.

But the U.S. Attorney’s Office mentioned the indictments against the three men and Zapata Espinoza in a notice to the federal court on June 24. The notice said a court reporter had accidentally taped over the April 19 grand jury testimony of an FBI special agent in the investigation into the attack on Zapata and Avila. Zapata was a native of Brownsville.

The U.S. Attorney’s Office said in the notice that because the erasure had been an unintentional error, prosecutions of the four men who were indicted should not be affected. The U.S. Attorney’s Office also stated that it did not foresee calling the FBI agent as a witness in any trial, meaning the testimony would not be discoverable; in other words, it would not have to be provided to the defense.

According to the court record, a federal rule requires that grand jury proceedings be recorded by a court reporter or recording device. The U.S. Attorney’s Office maintains that the rule also states that the validity of prosecutions is not affected by the unintentional failure to make a recording.

The court record does not indicate if the court has responded to the U.S. Attorney’s Office notice.

The four suspects mentioned in the notice of the U.S. Attorney’s Office also were listed by the Mexican Attorney General’s Office among those arrested in Mexico after the attack on Zapata and Avila.

Zapata and Avila were attacked Feb. 15 by two suspected hit squads of the Zetas drug cartel, the U.S. Attorney’s Office states in court records.

The record says the two hit squads, or “estacas,” were comprised of eight armed Zetas members who forced the agents’ vehicle off the highway and ordered the agents out. As the agents attempted to identify themselves as U.S. diplomats, the attackers opened fire.

As reported earlier, the two agents had been assigned to the ICE attaché office at the U.S. Embassy in Mexico City and were traveling on official business in a vehicle bearing diplomatic plates in the state of San Luis Potosi when they were attacked.

Following the arrest of Zapata Espinoza, the Mexican Attorney General’s Office said he had confessed to being the leader of a Zetas cell in San Luis Potosí and also to having led the attack on the two U.S. agents.

The Mexican Attorney General’s Office said Zapata Espinoza maintains that confusion led to the attack on the agents because his Zetas group believed that a rival group was in the vehicle. Zapata Espinoza later recanted and claimed that Zapata and Avila had provoked the encounter.

The federal court record regarding Zapata Espinoza’s indictment states that he was a member of one of the hit squads involved in the attack.

The court record states that the investigation continues and that much of the evidence and many witnesses to the attack remain in Mexico. Several of the members of the hit squads remain at large, the documents indicate. Zapata Espinoza is being held without bail.