CIUDAD VICTORIA, Mexico >> The anonymous tip that led Mexican authorities to a remote shack where four abducted Americans were held described armed men, people wearing blindfolds and plenty of activity around a ranch.

Authorities headed for the rural area east of Matamoros on Tuesday morning, leaving the highway and driving remote dirt roads looking for the described location, according to Mexican investigative documents viewed today by The Associated Press.

Finally, they saw the wooden shack far from any homes or businesses, surrounded by brush, and a white pickup parked outside that matched the one the Americans had been loaded into on March 3. Then they began to hear someone shouting, “Help!”

Inside the shack, the documents said, Latavia “Tay” McGee and Eric Williams were blindfolded. Beside them were the bodies of Shaeed Woodard and Zindell Brown, wrapped in blankets and plastic bags. When authorities arrived, McGee and Williams shouted desperately to them in English.

A guard who tried to escape out a back door was quickly apprehended, the documents said. He was wearing a tactical vest, but there is no mention of him being armed.

The four Americans had crossed into Matamoros from Texas so that McGee could have cosmetic surgery. About midday, they were fired on in downtown Matamoros and then loaded into the pickup truck. Another friend, who remained in Brownsville, called police after being unable to reach the group that crossed the border. A Mexican woman, Areli Pablo Servando, 33, was also killed, apparently by a stray bullet.

In the letter obtained by The Associated Press through a Tamaulipas state law enforcement official Thursday, the Scorpions faction of the Gulf cartel apologized to the residents of Matamoros where the Americans were kidnapped, Servando, and the four Americans and their families.

But relatives of the abducted Americans said that the purported apology has done little to dull the pain of their loved ones being killed or wounded.

Woodard’s father said he was speechless upon hearing that the cartel had apologized for the violent abduction captured in video that spread quickly online.

“I’ve just been trying to make sense out of it for a whole week. Just restless, couldn’t sleep, couldn’t eat. It’s just crazy to see your own child taken from you in such a way, in a violent way like that. He didn’t deserve it,” James Woodard told reporters Thursday, referring to his son’s death.

The cousin of Williams, who was shot in the left leg during the kidnapping, said his family feels “great” knowing he’s alive but does not accept any apologies from the cartel.

“It ain’t gonna change nothing about the suffering that we went through,” Jerry Wallace told the AP on Thursday. Wallace, 62, called for the American and Mexican governments to better address cartel violence.

U.S. Ambassador Ken Salazar told reporters today that U.S. officials had contacted President Andrés Manuel López Obrador directly over the weekend to ask for help in locating the missing Americans in Matamoros. He said the cartel there “must be dismantled.”

The letter attributed to the cartel condemned last week’s violence and said the gang turned over to authorities its own members who were responsible.

“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 individuals had gone against the cartel’s rules, which include “respecting the life and well-being of the innocent.”

A photograph of five bound men face-down on the pavement accompanied the letter, which was shared with The Associated Press by the official on condition that they remain anonymous because they were not authorized to share the document.

A separate state security official said that five men had been found tied up inside one of the vehicles that authorities had been searching for, along with the letter. That official also spoke on condition of anonymity because they were not authorized to speak about the case.

Tamaulipas state prosecutor Irving Barrios said, today, via Twitter that five people related to the violence had been arrested on charges of aggravated kidnapping and homicide. He said only one other person had been arrested in recent days.

Contributing to this report were Associated Press writers Mark Stevenson in Mexico City and Acacia Coronado in Austin, Texas.