When he began receiving the calls from frantic family members that his daughter and four of his grandchildren had been killed on a rocky stretch of road in the Sierra Madre mountains last month, Adrian LeBaron didn’t wait for local law enforcement. He drove in search of the crime scene, and began his own investigation.

He and his wife were the first to arrive on the desolate highway where hitmen working for drug cartels had brutally massacred their daughter Rhonita Miller and eight others from a cluster of Mormon communities where the LeBarons live in northern Mexico.

Pausing to put on rubber gloves so as not to erase fingerprints or other vital crime scene markings, LeBaron, 59, began the grisly task of digging through the ashes of his daughter’s burnt-out, blackened SUV. Choking back tears, he and his wife Shalom, 56, carefully took photographs of what was left of their loved ones, sifting through pieces of bone and ash and gathering up dozens of shell casings from AR-15 and M-16 assault rifles they found next to the still-smoldering vehicle, the charred remains of their family members visible inside.

They found the bones of their 10-year-old granddaughter Krystal, who had been so scared she squeezed her body into a fetal position just before she was shot. Miller, 30, was shot multiple times, and died along with the four of her seven children who were with her in the car, including 8-month old twins, Titus and Tiana. The youngest victims of the massacre, they likely were burned alive.

“When we picked up those shells so close to the car, we knew that our family had been shot at close range,” LeBaron told The Post Friday. “They had clearly been targeted.” LeBaron said the family and other Mormon clans have long been in the crosshairs of the cartels because they refuse to get out of their way.

And LeBaron, despite his unspeakable losses and the constant danger that surrounds him, defiantly continues his stand. In fact, he has taken the fight to the cartels on several fronts — planning to form armed militias, and lobbying both Washington and Mexico City for stronger enforcement of the cartels.

He and other Mormons in the northern part of the country want to join forces with local law enforcement in wild west-style volunteer militias — “like posses,” he said — that would act as a wall of defense against the traffickers. In order to avoid corruption, LeBaron wants municipal police to be independent, and not beholden to local mayors who have been bought off by the cartels.

“The Mexican municipal police are not autonomous in this area,” said LeBaron. “They are under the control of the mayors, who are financed by the cartels.” Among the crime syndicates in the region is the Sinaloa cartel, once controlled by Joaquin “El Chapo” Guzman, who is now serving out a life sentence in the US.

“The old ways here have to change,” said LeBaron. “We have 20 neighboring municipalities and no district attorney. We have no independent police, and that has to change.”

He went to Washington, D.C., to lobby US officials to recognize the drug cartels as terrorist organizations, which would allow the feds to freeze their US assets. And last month, his family led a march against violence in Mexico City.

This cartel attack against women and young children was by far the deadliest in a battle for control of the outback territories in Chihuahua and Sonora states near the US border where criminal gangs transport drugs to the US.

“The traffickers want to get rid of the gringos,” LeBaron told The Post. “They want to turn our communities into ghost towns.”

But LeBaron and the 5,000-strong Mormon communities in northern Mexico say they aren’t going anywhere. They are US/Mexican nationals who have lived in these northern states for generations. The clans are descendants of fundamentalist Mormons who settled in Mexico after 1890 when the US government began to put restrictions on polygamy. Adrian LeBaron has 35 children, 85 grandchildren and at one point had four wives, he told The Post.

While LeBaron and many of the men in his family work in the US, he speaks English with a Mexican accent and sometimes fumbles for the right word. He has lived his whole life in Mexico, long enough to know that local authorities cannot be trusted.

So when LeBaron and his wife finished gathering their evidence, they got back into their own SUV and drove five hours north to Arizona, handing their findings to the FBI, the only lawmen they could trust.

One of the findings was “that they had been robbed,” LeBaron said. He and his wife found a checkbook and other articles strewn from Miller’s purse on the ground near her burned-out car.

After the Nov. 4 massacre that left three women and six children dead, Mexican state and federal police took more than 24 hours to arrive on the scene, and forensics investigators didn’t show up until 30 hours after the bodies were found. No yellow police tape ever closed off the two crime scenes, which were 12 miles apart as hitmen targeted the convoy of three SUVs all driven by women, said Le Baron.

When the FBI offered to help with the probe, the Mexican federal government first barred them from crossing the border, a US federal source told The Post.

“About a week later, they finally let in the FBI, but they could not be armed,” said LeBaron, adding that the agents had to follow strict Mexican government protocols that prohibited foreign investigators from identifying themselves as US law enforcement in the country.

“We know that if we want justice, we just have to do it ourselves,” LeBaron told The Post. “And I won’t stop until I get it.”

LeBaron, along with representatives from the other families who lost loved ones in the massacre, haven’t stopped working for justice since they buried their families last month.

After meeting with the FBI in the days after the massacre, LeBaron and dozens of members of his family traveled to Washington, DC, and to Mexico City where they met with government officials, including the Mexican president. In Washington, they sought the aid of two Republican senators, Republicans Rick Scott and Mike Lee, and Democratic Utah Rep. Ben McAdams, to press the federal government to declare cartels terrorist organizations.

President Trump initially backed the move, but then said he was temporarily holding off at the request of Mexican President Andres Manuel Lopez Obrador. Undaunted, the LeBarons and the other families have started an online petition to push through with the terrorist designation.

“I was heartbroken for Mexico,” said Adriana Jones, 35, one of LeBaron’s daughters and Miller’s older sister who accompanied her parents to their meetings with government leaders. “The amount of people in that [Mexico City] march that came up to me and told me that their family members were also murdered, begging us to be their voice, telling us nobody would listen to them just broke my heart.”

There were 33,341 homicide investigations in Mexico last year, most of them related to drug cartels. This year’s total is expected to top 35,000, according to government statistics. Even so, Mexico’s left-wing president refuses to use violence against the drug traffickers, famously advocating “hugs not bullets” to stop the scourge. In October, AMLO, as he is known in Mexico, ordered police in Sinaloa to release from custody Ovidio Guzman Lopez, one of El Chapo’s sons, to avoid a further escalation of the war with the cartel.

Although Mexican authorities recently announced that they have arrested at least three suspects in the Mormon massacre, no other details have been made public.

Last week, LeBaron returned to the Mexican capital to meet with federal investigators who asked him to obtain the titles to the three vehicles that were burned in the attack.

“We appreciate that they are trying to gather evidence, but I don’t know why they have asked for that,” he said. “My feeling about the Mexican authorities is that they are not super heroes. There’s a great deal of ineptitude.”

LeBaron knows that change may take a long time. Many Mormons in the region no longer have the patience, he admitted, and have left the country in the weeks after the massacre. Among them are his grief-stricken son-in-law, Howard Miller, and his three surviving children Tristan, 8, Amaryllis, 5, and Zack, 3.

“I’m not leaving,” said LeBaron. “I owe it to Rhonita and my grandchildren to stay and fight. If I have to tell their story a million times for the next 20 years in order to live in peace, I will.”