HOUSTON -

A routine arrest for breaking into cars has exploded into a surprise investigation of drug cartel killings across the border in Mexico, Local 2 Investigates reported Wednesday.

Deputy constables said they got a call that someone was breaking into cars at the Walmart on I-10 at Freeport last month. Officials said they quickly arrested a man who was caught in the act.

Shortly after his arrest, Alfredo Nunez Cantu, 37, of Corpus Christi, told deputies he had been involved with at least two killings on behalf of the notorious Zetas drug cartel.

According to law enforcement officers who were present for his questioning, Cantu told FBI agents that he was a member of the La Rasa Unidad gang in Corpus Christi, and he said the Zetas cartel instructed him to coordinate the killing of two local men as they were across the border in Mexico.

FBI agents arrived at the Harris County Jail to question him about the international cartel killings, but no charges have been filed.

On the car burglary case, Nunez pleaded guilty within days of his arrest. He is serving a 210-day sentence in the Harris County Jail.

He has prior convictions for felony escape and felony assault, both of which landed him in a Texas prison in the mid 90's.  He also has drug convictions and several theft convictions, according to Harris County District Clerk records.