Officials in Mexico have arrested a man suspected of involvement in the brutal killing of the mayor of Chilpancingo last month.

The killing of Alejandro Arcos, whose decapitated body was found just days after he was sworn in as mayor, caused shock and revulsion in the violence-torn state of Guerrero.

On Tuesday, police detained Germán Reyes, Chilpancingo’s top security official, for his alleged role in the murder.

Germán Reyes denied any involvement in the murder and said he was being used as a scapegoat.

Rights groups have long warned that Mexico’s local security forces are infiltrated by powerful criminal gangs, who bribe, blackmail and threaten local officials into compliance.

The brutal killing of Mayor Arcos, a week after taking office on October 1, and Tuesday’s arrest of Reyes are seen by many in Chilpancingo as further evidence of attempts by local criminal groups to tighten their grip on the city and authorities its.

The fact that Reyes – a retired army captain who led the Guerrero state prosecutor’s office for serious crimes before taking over as Chilpancingo’s acting security chief – was named the prime suspect in the mayor’s killing sent new shock waves through the city .

Much of the violence in Chilpancingo is blamed on a bloody battle between a criminal gang called Los Ardillos and the rival local crime group Los Tlacos.

Los Ardillos specialize in drug trafficking in the state of Guerrero, but have reportedly expanded into extortion and other lucrative criminal enterprises.

Its members also attempted to gain control of the city’s security forces.

According to Mexican Security Minister Omar García Harfuch, Mayor Arcos was traveling to an area controlled by Los Ardillos unaccompanied and without a security detail “for a meeting” when he was killed.

Prosecutors have so far offered few details about why they suspect Germán Reyes of involvement in the murder.

Reyes told a judge he had “no reason” to harm the mayor, saying Mayor Arcos appointed him the city’s security chief.

Meanwhile, the federal government has sent more than 12,000 soldiers and National Guard members to the state.

Confronting the wave of violence in Guerrero and other hotspots of cartel and gang violence is one of the main challenges facing President Claudia Sheinbaum, who took office on October 1.

During his presidential campaign, Sheinbaum dismissed the “militaristic” approach of former Mexican President Felipe Calderón — who declared war on the cartels in 2006 — as ineffective.

She instead vowed to continue the approach of her immediate predecessor, Andrés Manuel López Obrador, who avoided direct confrontation with the cartels, arguing that it only led to more bloodshed.

Since being sworn in as president, she has said her government will work to solve crimes and combat widespread impunity by creating a national intelligence system.