A Mexican general and his wife were killed by gunmen on Saturday as they were driving in Vallecillo in the northern state of Nuevo Leon.

General Ricardo Cesar Nino Villarreal was one of four military personnel sent in May by the Mexican government to quell violence from the drug cartels in the state of Tamaulipas, according to a report from AFP. He and his wife were killed Saturday, but their bodies and bullet-riddled two-door car weren't found until Sunday. More than 100 high-caliber bullet casings were found around the scene of the murder.

Authorities have yet to say who they suspect committed the murders.

"The government of Tamaulipas condemns and deeply laments the death of General Ricardo Cesar Nino Villarreal and his wife," the state's security coordination group said in a statement.

Nino Villarreal was tasked with taking charge of a northern area that includes Nuevo Laredo, a city where drug cartels have been fighting for years, trying to establish control of the valuable drug-trafficking route.

Adrian de la Garza, Nuevo Leon's chief prosecutor, said that Nino Villarreal typically travelled in an armored car to protect him from such attacks, but the general was unarmed and in his civilian vehicle when he was attacked.

Nino Villarreal survived an attack just last month when unidentified gunmen shot at his armored vehicle in Linares, which is also in Nuevo Leon.

Prior to his appointment in Tamaulipas, Nino Villarreal served as the chief of police in the Nuevo Leon town of Cadereyta. He was appointed to secure Tamaulipas when the military took over the town in May, after dozens of people died in battles between the warring drug cartels and firefights between authorities and the drug gangs, according to France 24.

The fighting in recent years has been blamed on the Zetas and Gulf drug cartels. Both have seen their power diminish as top leaders have either been killed or arrested. Infighting within the Gulf cartel is the cause of the most recent uptick in violence.