A Mexican drug cartel claiming its members were behind the brazen kidnapping of four Americans last week handed over five of the members and left a note of apology, Mexican media outlets and The Associated Press reported Thursday.

Photos circulating on social media show five men on the pavement with their hands tied – four of them shirtless – in front of a pickup truck, which has a handwritten letter of apology on the windshield.

The AP reported obtaining a copy of the letter from a law enforcement source in Tamaulipas, the Mexican state where the American travelers were attacked. Two of them were killed and another one wounded in a shooting Friday shortly after arriving in the border city of Matamoros for cosmetic surgery.

Authorities have said cartel members probably mistook them for drug smugglers and abducted them after shooting their van.

In the letter, the Scorpions faction of the Gulf cartel apologized to the residents of Matamoros, a Mexican woman who was killed by a stray bullet and the four Americans and their families.

“We have decided to turn over those who were directly involved and responsible in the events, who at all times acted under their own decision-making and lack of discipline,” the letter reads, adding that those people had gone against the cartel’s rules.

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The AP also obtained the photo of the men face-down on the ground and reported that they had been found tied up inside one of the vehicles authorities had been seeking, along with the letter, according to an official not authorized to speak about the case.

Bodies returned to US authorities

Tamaulipas officials have not publicly confirmed having new suspects in custody, but earlier Thursday the attorney general’s office said it had seized an ambulance and medical clinic in Matamoros that were used to provide first aid to the injured Americans.

Authorities located them Tuesday morning on the outskirts of the city, guarded by a man who was arrested. Zindell Brown and Shaeed Woodard died in the attack; Eric Williams survived with a leg wound and Latavia McGee was physically unharmed.