La nota, que supuestamente habría sido escrita por un cártel poderoso, indicaba que los hombres que atacaron a los estadounidenses actuaron por cuenta propia.
The note, which was purportedly written by a powerful drug cartel, apologized for the attack last week that left three people dead, and offered up five men it said were responsible.
The four came under fire shortly after entering the city of Matamoros from Brownsville, Texas. The F.B.I. is offering a $50,000 reward for their return and the arrest of the kidnappers.