A former prosecutor and local police official was arrested Tuesday in connection with the grisly decapitation of a mayor on Oct. 6.

Officials in the southern state of Guerrero confirmed that Germán Reyes was arrested on charges of homicide for the killing of Alejandro Arcos just a week after he took office as mayor of the state capital, Chilpancingo.  The public prosecutor’s office in Guerrero released a photo of the suspect, identifying him as German “N” in line with the usual practice of not giving full names.

The arrest was shocking, because officials had previously blamed the killing on a local drug and extortion gang, and Reyes was formerly employed as special prosecutor for Guerrero state, a high-level position.

The implication was that Reyes – who was also a former military officer who, according to his official resume, retired with rank of captain in the military justice system – had somehow worked in collusion with the gang.

That would suggest that at least one of the two warring gangs fighting for control of Chilpancingo controls, intimidates or works with officials there.

If Reyes is convicted, it would also be a stinging rebuke for a policy adopted by cities across Mexico of hiring retired military officers for top local police jobs, on the assumption that they are less prone to corruption.

It was also revealing that state detectives had to rely on federal forces – soldiers and the National Guard – to make the arrest, suggesting they may not have trusted state and local police who would normally carry out such tasks.

It was not clear what title Reyes held in the Chilpancingo municipal security force, or whether he served both under Arcos or the replacement mayor who took office after he was killed. Four mayors from other towns in Mexico requested protection a day after Arcos’ remains were found.

Mexico’s top federal security official, Omar García Harfuch, said earlier Tuesday that Arcos -the mayor whose body was found in a pickup truck, with his severed head placed on the roof of the vehicle – was apparently killed by the same gang responsible for killing 11 market vendors, including four boys, last week.

The vendors, members of an extended family, were abducted in late October as they traveled to sell their wares. Their bodies were found dumped in the bed of a pickup truck on an avenue in Chilpancingo last week.

While neither Harfuch nor state prosecutors would name the gang, a local human rights activist said the Ardillos were responsible for killing the market vendors.

The activist, who did not want to be quoted for fear of reprisals, said the Ardillos gang controlled large parts of the state and had state congressmen and other officials working for them.

The Ardillos have been locked in a years-long battle for control of Chilpancingo with a rival gang, the Tlacos. That turf battle has left mutilated corpses strewn around the city in recent years.

Mexican cartels frequently dump bodies of their hostages — or post grisly videos of torture, interrogation and decapitations of their victims — to intimidate their rivals and authorities. Messages are often left on victims’ bodies by cartels seeking to threaten their rivals or punish behavior they claim violates their rules.

Chilpancingo, a city of about 300,000, is so completely dominated by gangs that in 2023, one of them staged a demonstration of hundreds of people, hijacked a government armored car, blocked a major highway and took police hostage to win the release of arrested suspects.

Violence in Guerrero reached such unprecedented levels that earlier this year, Roman Catholic bishops announced they had helped arrange a truce in another part of the state between two warring drug cartels.

At the time, former president Andrés Manuel López Obrador- who refused to confront the gangs – said he approved of such talks.

“Priests and pastors and members of all the churches have participated, helped in pacifying the country. I think it is very good,” said López Obrador, who left office Sept. 30.

Agence France-Presse contributed to this report.