In what could be third recent case of alleged abuses by security forces, ‘Hercules’ unit is implicated in deaths of Erica Alvarado Rivera and her two brothers

Authorities are investigating a possible police connection to the killing of three US citizens visiting their father in Mexico who were found shot to death along with a Mexican friend more than two weeks after going missing.

Parents of the three siblings, whose bodies were identified Thursday, have said witnesses reported they were seized by men dressed in police gear calling themselves “Hercules”, a tactical security unit in the violent border city of Matamoros heavily racked by cartel infighting. Nine of the unit’s 40 officers are being questioned, Tamaulipas state attorney general Ismael Quintanilla Acosta said.

It would be the third recent case of alleged abuse and killings by Mexican security forces and the first to involve Americans.

The country already is engulfed in the case of 43 teachers college students missing in southern Guerrero state at the hands of a mayor and police working with a drug cartel. Fifty-six people are under arrest, including dozens of police officers. In June, soldiers killed 22 suspected gang members in Mexico state, then altered the scene and intimidated witnesses to hide the fact that most of the dead were executed after they surrendered, a National Commission on Human Rights report said last week. Three soldiers face murder charges.

“We will apply the full force of the law and zero tolerance,” Tamaulipas governor Egidio Torre Cantu said, lamenting the death of the three Americans and a Mexican citizen, even though their identities had yet to be confirmed by DNA.

Presidential spokesman Eduardo Sanchez declined comment when asked about the newest case. The US embassy said it was aware of the reports but had no information to share “due to privacy considerations”.

The father of the three Americans, Pedro Alvarado, identified his children from photographs of the bodies showing tattoos, Quintanilla told Radio Formula. Clothing found with the bodies also matched that of Erica Alvarado Rivera, 26, and brothers, Alex, 22, and Jose Angel, 21, who disappeared 13 October along with Jose Guadalupe Castaneda Benitez, Erica Alvarado’s 32-year-old boyfriend.

Facebook Twitter Pinterest Erica Maria Alvarado Rivera and her brother Alex at their mother’s home in Progreso, Texas. Photograph: AP

Each was shot in the head and the bodies were burned, most likely from lying in the hot sun for so long, Quintanilla said.

Tamaulipas authorities said it could take 24 to 48 hours for DNA tests to confirm that the bodies were those of the Alvarado siblings, who were last seen in El Control, a small town near the Texas border west of Matamoros, about to return home to Progreso, Texas.

“They were good kids,” said an aunt, Nohemi Gonzalez. “I don’t know why they did that to them.”

The three siblings shared their mother’s modest brick home on a quiet street in Progreso less than three miles from the border. Erica, who has four children between the ages of three and four, had been scheduled to begin studying to become a nursing assistant next month.

Brothers Jose Angel and Alex had been scheduled to make their annual pilgrimage to Missouri as migrant farm workers more than a week ago, Gonzalez said. When they weren’t on the road, they divided their time between their mother’s house in Texas and their father’s Mexico.

Officials have not commented on the events that led up to the disappearances, but the families’ informal inquiries produced this version:

On Sunday, 12 October, Erica drove her black Jeep Cherokee across the border to El Control. She dropped it at her father’s house and went to visit with her boyfriend.

Her mother, Raquel Alvarado, had told her to be back in Progreso by early Monday morning, because Raquel had to work and Erica’s kids had to get to school. Raquel put the kids to bed Sunday night and awoke at 4am to see Erica was not home. She began calling her daughter’s cellphone, but got no answer. At that point, it appears Erica was fine.

She continued calling through the morning of 13 Ocober. “I’m always worried about her when she goes over there,” the mother said.

Around 1pm, she reached her former husband. He told her Erica had called her brothers and asked them to bring her Jeep to a roadside restaurant under a bridge near El Control where she was eating with her boyfriend. One brother drove her Jeep and the other drove his Chevrolet Tahoe because they all planned to return to Progreso from there.

According to Raquel Alvarado, witnesses told family members that the brothers arrived around 12:30 p.m. and saw members of the police unit called Hercules pushing their sister and Castaneda and hitting Erica. When the brothers intervened, the police took all four of them, along with their vehicles. The witnesses said the armed men identified themselves as members of the Hercules unit and warned against intervening.

A September news release from the city about Hercules showed an armed force in fatigues and face paint. Mayor Leticia Salazar officially introduced Hercules as a group with particular skills to confront crime in high-risk operations. They have passed background checks and are trained by the state, Quintanilla said.

Neither Salazar nor the city’s spokeswoman returned messages seeking comment Thursday.