(CNN) -- It would have been one of the most audacious plots between a Mexican drug cartel and American conspirators: a murder-for-hire in South Texas.
But the men who allegedly were prepared to use their U.S. military training to carry out a mission in Laredo, Texas, for the Zetas drug cartel were not actually making arrangements with drug traffickers. They had walked into a Drug Enforcement Administration sting operation, and were plotting with undercover agents who recorded their every move for months.
Their alleged criminal plans fell apart on Saturday, the day they were to carry out a contract killing. The agents had the evidence they needed and arrested three men in Laredo. A fourth was killed by agents as the arrests were being made. Two more arrests were made in South Carolina. A sixth man also was arrested, the DEA said.
The Zetas and other drug cartels are known to have corrupted U.S. officials in the past, usually border guards or military who allow the traffickers to get contraband across the border and through checkpoints. There is no evidence the Zetas have considered escalating their reach to include hiring Army-trained Americans to carry out killings. But these arrests show it is not beyond the realm of possibility that there are U.S. citizens willing to do such work.
The three men accused of being at the center of the operation -- Kevin Corley, Samuel Walker and Shavar Davis -- had military experience and training they were willing to use on behalf of a drug cartel, prosecutors say.
A criminal complaint filed in federal court points to Corley, a former Army 1st lieutenant, as the leader. He was discharged from the military this month.
Walker is a sergeant on active duty based at Fort Carson, Colorado. Both belonged to the 2nd Battalion, 12th Infantry Regiment, 4th Brigade Combat Team, 4th Infantry Division, a Fort Carson spokeswoman said.
Davis was a private in the Army Reserves for six months between 2004 and 2005.
According to the criminal complaint, Corley was introduced to the agents posing as Zetas by two men, Marcus Mickle and Calvin Epps. As far back as January 2011, Mickle began negotiating with the undercover agents to move large quantities of marijuana to South Carolina. As the agents began reeling in the pair with promises of 500 pounds of pot, Mickle and Epps upped the ante, the complaint states.
They knew an active duty army officer, Corley, who was offering to train cartel members in tactics including approaches, room clearing, security and convoy security, court documents say.
According to the complaint, Corley promised the undercover agents that weapons could be easily stolen from military posts, and that he could train 40 cartel members in two weeks. He mailed an Army tactical book to the agents, the court document says.
The investigation appears to have risen to another level when Corley said he could assemble a team to carry out cartel dirty work.
The agents posed a scenario to him: Would Corley be willing to raid a rival cartel's ranch and recover 20 kilos of stolen cocaine?
According to the complaint, Corley answered that he would do it for $50,000 and 5 kilos of cocaine.
The two sides set a date of March 24 for the operation, the court document states.
Corley arrived in Laredo with his cousin, Jerome Corley, Walker and Davis, along with two AR-15 assault rifles, a training rifle, and five allegedly stolen ballistic vests, the complaint states.
According to the complaint, "Corley told the undercover agent he had bought a new Ka-Bar knife to carve a 'Z' into the victim's chest and was planning on buying a hatchet to dismember the body."
On the day the supposed hit was to take place, the agents had the four confirm they understood they were about to accept money and drugs in exchange for a killing, the court document states. Then other agents came in to make the arrests.
One of the agents shot and killed Jerome Corley, though details were not disclosed in the document.
Mickle and Epps, the pair who made the introductions, were arrested in South Carolina. The DEA identified the sixth man arrested as Mario Corley.