The leader of the hitman group “Tropas del Infierno” (Troops from Hell) and the Cartel del Noreste (Northeast Cartel) was arrested by Mexican authorities on March 13 in Nuevo Laredo, Mexico, the sister city to Laredo, Texas.

The arrest of Juan Gerardo Treviño Chavez, also known as “El Huevo,” sparked a gunfight, blockades, and explosions in the early morning hours of Monday just across from the U.S. border.

“El Huevo” was one of U.S. Customs and Border Protection’s most wanted criminals.

Mexico had issued warrants for his arrest listing extortion, organized crime, intentional homicide, and terrorism. The Tamaulipas government offered a $100,000 reward to anyone who provided information leading to his arrest.

In the U.S., Treviño Chavez faces charges for drug trafficking and money laundering. As a U.S. citizen, he will be extradited to the U.S. to face them. Currently, he is being held in a detention facility in Mexico by the Special Prosecutor’s Office for Organized Crime.

Mexican federal authorities, including the Secretary of the National Defense, Attorney General of the Republic, The National Intelligence Center, and the Mexican National Guard, all collaborated to apprehend the suspect.

At the time of his arrest, he allegedly had two firearms exclusively issued to the Mexican Army and Air Force in his possession.

After “El Huevo” was taken into custody, Mexico deployed additional military personnel in Nuevo Laredo, anticipating retaliation. As the military personnel patrolled Laredo’s sister city, gunfights broke out among suspected gang members, resulting in multiple pursuits and confrontations.

According to a statement from the ministry of public security in Tamaulipas, gang members blocked traffic by placing spike strips and setting fire to trailer trucks at two main avenues in the city. The U.S. Consulate and Mexican military bases took damage from gunfire.

“In view of the unfortunate events that occurred early Monday morning in the city, we ask everyone to exercise extreme caution. Some roads are still inaccessible,” the mayor of Nuevo Laredo Carmen Lilia Canturosas said on Facebook at 6:56 a.m. on March 14. “I am in constant communication with federal and state authorities, and I will keep you informed. God bless Nuevo Laredo.”

The U.S. consulate advised its employees to “shelter in place” and asked U.S. citizens to do the same and avoid the area. Later, the Mexican government released a statement saying that the consulate would remain temporarily closed to the public.

“Due to reports of gunfire overnight near the U.S. Consulate and in locations throughout Nuevo Laredo, U.S. gov. employees have been advised to continue to shelter in place. U.S. citizens should avoid the areas or continue to shelter in place,” the U.S. Consulate General said on Facebook at 8:47 a.m.

A senior Mexican official told Reuters that at least one “collateral” fatality occurred due to the violence.

The gunfire could be heard across the border in Laredo, Texas, prompting Laredo Police to temporarily block access to the international bridges that cross into Nuevo Laredo.

“For public safety reasons, southbound traffic into Nuevo Laredo at Juarez-Lincoln Bridge and Gateway to the Americas Bridge had been temporarily suspended due to an ongoing security situation on the Mexico side. Southbound traffic fully resumed at both bridges at approximately 7:30 a.m. (Monday) morning,” a Customs and Border Patrol (CBP) official said.

Access was restored later that morning.

“The arrest of Juan Gerardo’ N’ (alias) ‘El Huevo’ represents a blunt blow to the dome of power of the Cartel Del Noreste,” the Mexican Army said in a statement.

The Northeast Cartel is known to have a presence in Nuevo Laredo, the Mexican city of Monterrey, and the Mexican state of Nuevo León, and additionally operates a dangerous network in Texas, according to the Tamaulipas Attorney General’s Office.