Mexican police have nabbed a top leader of the feared Zetas drug cartel, authorities said Monday. Police arrested Jesus Enrique Rejon Aguilar, who was wanted in the murder of a US Immigration and Customs Enforcement official, on Sunday, the Public Safety office said. Rejon Aguilar, the third-ranking cartel official and one of its founders, was arrested in Atizapan de Zaragoza, in Mexico state, the office added. He was sought in connection with a February 14 attack in San Luis Potosi state that left the US agent, Jaime Zapata, dead and left his partner seriously wounded. The news came after the southwestern US state of Texas warned Americans to avoid the Mexican border town of Nuevo Laredo over the July 4 independence day weekend, fearing that US citizens will be targeted. Texas state and local police have \"received credible intelligence from multiple sources that indicates the Zetas Cartel is planning to target US citizens who travel to Nuevo Laredo this weekend,\" the Texas Department of Public Safety said in a statement. Nuevo Laredo is located in the Mexican state of Tamaulipas on the Rio Grande river, which serves as the international border, across from the Texas border city of Laredo. Mexico\'s Zetas drug cartel is also accused of two mass killings in Mexico\'s northeastern state of Tamaulipas. The Zetas was founded by Mexican army Special Forces deserters in the 1990s who were hired as hitmen for the powerful Gulf cartel. The group later split from their employers, sparking bloody Mexican turf wars. They are strongest in eastern Mexico and the northern border states of Tamaulipas and Nuevo Leon. The Zetas were among the first Mexican crime syndicates to use heavy weaponry and full-scale military tactics, reportedly amassing an arsenal that has included grenade launchers and even ground-to-air missiles. Some 37,000 people have been killed in mainly drug-related feuds since President Felipe Calderon launched a military crackdown four years ago involving some 50,000 troops and police reinforcements that has so far failed to stem the bloody tide of violence.