MEXICO CITY — They have gone down with guns blazing on country roads and in opulent mansions, more quietly while sleeping in seaside condominiums and even, most recently, while dining in fine restaurants. But their downfalls have almost always occurred in Mexico.

Now comes the arrest of a man whom the authorities in Mexico and the United States describe as the leader of a major drug trafficking gang — while he was shopping in Texas.

Juan Francisco Sáenz-Tamez, 23, who American officials said led the Gulf Cartel after clawing his way to the top only last year, was arrested Oct. 9 while shopping in Edinburg, Tex., just over the border from Reynosa, Mexico, a violent industrial city that was his base, the officials said. A 2013 indictment charging him with conspiring to traffic cocaine and marijuana into the United States and launder millions of dollars there was unsealed Tuesday in Federal District Court in Beaumont, Tex.

Crime analysts said it was unusual for suspected organized crime leaders from Mexico to be apprehended in the United States, although they are believed to visit just like thousands of law-abiding Mexicans.