Authorities remain perplexed as to the motive behind the abduction of four Americans by the Mexican Gulf Cartel after an apology letter was reportedly delivered along with the men responsible for the attack.

The cartel disavowed the violent abduction that left two Americans and a Mexican citizen dead in a letter obtained by the Associated Press. Along with the letter were five men with their shirts bound across their faces obscuring their vision and arms tied behind their backs. These men were later arrested by Mexican authorities.

The cartel alleges the group was responsible for the attack.

"The Gulf Cartel Grupo Escorpiones strongly condemns the events of Friday, March 3 in which unfortunately an innocent working mother died and four American citizens were kidnapped, of which two died," a translation of the letter says. "For this reason, we have decided to hand over those involved and directly responsible for the events who at all times acted under their own determination and indiscipline and against the rules in which the CDG has always operated."

Four U.S. citizens were assaulted and kidnapped on Feb. 3 near the Mexican border town of Matamoros after crossing from Brownsville, Texas.

Latavia "Tay" Washington McGee drove to Mexico with Shaeed Woodard, Zindell Brown, and Eric Williams for a medical procedure when their white minivan was intercepted and the group abducted. Woodard and Brown were killed sometime during the incident and their bodies returned to the U.S.

While the apology note seems odd for the reputation of the cartel, it is actually a common practice for these groups. In the face of intense scrutiny of their operations, and facing possible blowback from angered Americans, a note attempting to ease the tensions is believed to be a public relations move to displace the blame.

In its letter, the Gulf cartel noted its respect for the "life, tranquility and integrity of the innocent" and apologized to "the society of Matamoros ... the affected American individuals, and families."

"In addition the CDG asks society to remain calm because we are committed to ensure that these errors caused by indiscipline aren't repeated. The guilty parties will pay, regardless of who they are," the letter states.

The letter comes on the heels of a call to action on the Mexican drug cartels by Republican Sen. Lindsey Graham, who said the U.S. should "put Mexico on notice," during a Fox News appearance earlier this week.

"If you continue to give safe haven to drug dealers, then you are an enemy of the United States," said Graham.

This rhetoric was not well received by Mexican President Andrés Manuel López Obrador, as he brashly affirmed his country's position on the matter during a press conference Thursday.

"We are not going to allow any foreign government to intervene, much less a foreign government's armed forces," López Obrador told reporters according to the Hill.

"We are not a protectorate of the United States, nor a colony of the United States," he added. "Mexico is a free, independent, sovereign state."

Mexico U.S. Congress