Tuesday saw Mexican security forces digging near a garbage dump, excavating yet another unmarked grave with the hope of finally finding 43 student teachers who went missing after a protest last month amid reports of a massacre carried out by the local police.

And the hunt was continuing for the most wanted woman in Mexico, the woman said to have given the Iguala police chief a fateful order when she mistakenly imagined the students might disrupt a party she was throwing in honor of herself.

“Teach them a lesson.”

The order purportedly came from Maria de los Angeles Pineda Villa, wife of the mayor of Iguala and by numerous accounts the person really in charge.

“The key operator,” Sidronio Casarrubias Salgado of the Guerreros Unidos gang recently said of her status in the town’s underworld.

The purpose of the party was to celebrate Pineda’s many good works as the head of the town’s social-welfare agency and to kick off her campaign to succeed her husband, Mayor José Luis Abarca Velazquez.

On her Facebook page, the town’s real boss had already chronicled her efforts to provide new wheelchairs to the elderly, hearing aids to those who needed them, and assistance for handicapped children.

“The beautiful smiles to me are given away every day,” she wrote in Spanish below a photo of herself with a grinning special-needs youngster. “This is an incentive to continue running in the interest of society.”

And yes, Pineda had honored diligent teachers and top students.

“Many congratulations to all those masters and teachers,” she wrote. “We have all learned something good from them.”

Photos show her also holding the flag of the Red Cross and standing before five shiny new patrol cars she had secured for the local cops.

“In order to reinforce and ensure safety in the municipality,” she wrote.

What she did not report on Facebook was that she allegedly funneled more than $40,000 a month in bribes to the town cops and that she has extensive ties via her brothers to the Guerreros Unidos gang and to the Sinaloa cartel.

One thing the Iguala police are said to have ensured was that a good-size crowd gathered by 6 p.m. on Sept. 26 in the town’s Plaza of the Three Guarantees. The plaza is named after the Army of Three Guarantees that achieved the break with Spain, pledging to keep Mexico independent, unified, and loyal to the Catholic Church. Pineda stepped before the assemblage in a pink dress, holding a microphone and gazing upon them as if the fourth guarantee were fealty to her.

Pineda was just about to deliver her big speech extolling herself, to be followed by a big dance, when she was told that some outsiders were approaching. She apparently assumed they were protesters like the activists who had visited the town the year before.

In fact, the outsiders were student teachers who are said to have first gone to a nearby town, hoping to commandeer some buses in advance of a trip to Mexico City at the start of October for the annual remembrance honoring the hundreds of students massacred there in 1968.

After being thwarted in the other town, the student teachers had come to Iguala, and they had managed to secure a number of buses for the few days before the remembrance. They were rumbling past the square on their way back to their college when Pineda is said to have given her order.

By one account, the student teachers were on the road out of Iguala when their way was blocked by a pickup truck. Some of them are said to have gotten out and were pushing it aside when the police appeared, perhaps in those new patrol cars, directed by a special radio code used to signify that the order came from the mayor and his wife, “A-5.”

A female police officer is said to have shot a student in the head, and there was more gunfire in which a half-dozen innocents were killed. The police reportedly took the student teachers into custody and drove them away as instructed by the chief hitman of Guerreros Unidos, who is nicknamed Chucky.

The first flurry of gunshots did not disturb Pineda’s speech, which she seemed to consider a big success. She and her husband danced to the band in the plaza as the students were being tortured and shot in a remote place outside of town. Some are said to have been burned alive.

Too much of it seems to have been a replay on a larger scale of an incident back in May 2013. The trouble then had begun when some visiting activists had gotten into a verbal altercation with Pineda’s husband at a public forum. The husband had responded as if he were not only the mayor but the boss.

“Stop fucking around with me. I have people who work for me who can take care of this,” Mayor Abarca supposedly said.

The activist, an agronomist named Arturo Hernandez Cordona, is said to have replied. “What do you mean, ‘Take care of this’? That sounds like a threat to me.”

As later reported by the blog Borderland Beat, Hernandez and seven of his comrades were leaving town the following afternoon when their vehicle was stopped by men with guns. The men shot Hernandez in the right leg while pulling them all from the car. The activists were then blindfolded and driven to a field. The blindfolds were pulled away.

“We were looking at 10 men with rifles, and then the beating began,” the survivor would later testify.

Two of the gunmen dug a pit. A car pulled up and three men with beers climbed out, Abarca among them. The survivor could not quite identify the woman who remained shadowed in the car, though it is widely assumed that it was the actual boss, Pineda.

As the survivor tells it, Abarca approached Hernandez.

“You fucked with me, so I will have the pleasure of killing you,” Abarca supposedly told him.

Abarca allegedly battered Hernandez, who was then dumped in the pit. Abarca blasted him in the face and the chest with a shotgun.

One of the other activists attempted to escape and was gunned down. Abarca and his pals drove off, along with the woman.

At the moment when the remaining gunmen were distracted by a cellphone call, the five survivors bolted into the darkness. One was killed. Four managed to escape.

In the months that followed, those who demanded the Mexican federal government take action against the killers included the local head of the Catholic Church, Bishop Raul Vera Lopez. He practices a faith such as Mexico would do well guaranteeing, as evidenced when he caused a stir by baptizing the child of married lesbians.

“If I find the natural daughter of one of two women, how can I deny her baptism?” the bishop had said. “If the parents seek it, it’s because there is a Christian faith.”

He had added, “The church needs to come to them not with condemnation but with dialogue. We cannot cancel out a person’s richness just because of his or her sexual preference. That is sick, that is heartless, that is lacking common sense.”

The same spiritual sense prompted the bishop to seek justice for the slain activists. He traveled to Washington, D.C., and testified about the case before the Commission on Human Rights. He was no doubt including Iguala’s mayor when he condemned officials who “function as enemies to those who demand their rights.”

“Public servants?” the bishop asked. “Rather, butchers have come into power.”

In May, the head of Guerreros Unidos, Mario Casarrubias Salgado, aka the Beautiful Toad, was arrested. The Mexican government announced it had decapitated the organization that supplied much of the heroin to Chicago. His brother Sidronio immediately took over, and the Windy City reported no shortage of smack.

As for the killing of the activists, the only response from the Mexican authorities was to contend that the mayor had constitutional immunity from prosecution. The message for the murderers was that they could torture and kill with seeming impunity.

And that appears to have been their operating assumption when the 43 student teachers went missing. But the killers clearly failed to anticipate the uproar that would follow.

Even a government that has turned two blind eyes can hear the clamoring of tens of thousands of demonstrators. The authorities began to make arrests, including 22 cops who were apparently so corrupt that the cartel sought to have them freed by displaying a message known as a “narcomata.” It read:

“Release the 22 policemen. Or else we will reveal the names of all the politicians who work for us. The war is just beginning.”

But the government itself was not done. The new head of Guerreros Unidos was grabbed, and he reportedly told the authorities that Pineda was the one who gave the orders in town, including the order to teach the students a lesson.

A warrant was issued for her arrest along with her husband, who lost his immunity as he was now forced from office. Both fled, leaving their home with its razor-wire fence and windowless concrete façade, as well as their ranch and the 50-store shopping center they built, complete with food court. They were declared fugitives.

As of Tuesday night, the digging continued at the latest unmarked grave, previous digs having unearthed dozens of other murder victims but not the student teachers.

And Mexican’s most wanted woman was still at large. Her Facebook page remains up, and one lesson for all of us is that evil is at its starkest when it seeks to hide behind good deeds.