Authorities said Nichols also killed a federal customs agent, whose body was discovered Saturday.

CNN: Police: Manhunt marred by poor communication

Once they had identified Mr. Tsarnaev, a U.S. Customs agent entered his name into a Treasury terrorism database.

WSJ: U.S.: Russia Withheld Intel on Boston Bomb Suspect

But it all came to an end one morning in July, when he got stopped in Laredo, Tex. by a U.S. customs agent just as he was about to cross the Lincoln-Juarez Bridge into Mexico.

FORBES: Magazine Article

It is also necessary to be Mexican by birth to discharge the position of captain of the port and all services of practique and airport commandant, as well as all functions of customs agent in the Republic.

CENTERFORSECURITYPOLICY: Mexico's Glass House

"Historically, foreign wine has had to face a strong domestic-wine lobby, " says Pat Jones, an agent with the U.S. Customs Service.

FORBES: Magazine Article