The bodies of 25-year-old Brendan Mess and two other men were found with their throats cut on September 12, 2011, in what police deemed a triple homicide related to the drug trade.

Still-grieving relatives of the victims believe the men were killed the night before. And with word that Mess had once been the best friend and boxing partner of suspected Boston Marathon bomber Tamerlan Tsarnaev, it seems there might be more significance than anybody imagined in this triple slaying being committed on the 10th anniversary of 9/11.

The possibility that Tamerlan might have been involved also could help explain puzzling details of this unsolved crime that never fit with a ripoff or a drug deal gone bad.

The bodies were covered almost ceremoniously with marijuana. And $5,000 was found in the apartment. Also, there was no sign of forced entry, suggesting Mess knew the killer or killers.

One theory is that Tamerlan may have taken exception to Mess either giving or selling pot to his younger brother. Dzhokhar Tsarnaev was known to be an enthusiastic pot smoker. Mess seems to have been similarly fond of marijuana, as indicated by a tribute video posted after his death. The footage shows him taking a deep toke from what appears to be a joint at a summer pool party.

“Extra funky,” Mess says.

He appears in the clip to be much more a happy pot consumer than any kind of major dealer. He clearly views weed as an altogether wonderful thing and would not likely have thought he was doing anything wrong if he happened to share a little good cheer with a friend’s kid brother.

But the Tamerlan of late 2011 had turned so puritanically Muslim he would rail at fellow Muslims as “kafirs,” or nonbelievers, for suggesting that it is permissible to observe secular holidays such as the Fourth of July. He no doubt could have been roused to fury if a real kafir contributed to his younger brother preferring a-h-h-h-h to Allah.

If the evil weed was the issue, that might explain why the bodies were covered with it, as a kind of message. And the killer might not have wanted to compromise his supposed righteousness by stealing the $5,000.

Tamerlan did not attend Mess’s wake or funeral, even though they were supposedly best friends. One homicide detective sees this as an indication that Tamerlan was not involved in the killings, because he would not likely want to appear so guilty if he was in fact guilty.

But another investigator suggests that Tamerlan would almost certainly stay away from such kafir ceremonies if he thought Mess had corrupted his brother. This investigator notes that Tamerlan flew off to see his family in Dagestan three months after the killings, where he would sleep late into the afternoon in the way of some weighed down by troubles.

The investigators who still feel the killings arose directly from the drug trade note that the murdered trio also included Erik Weissman, who had been arrested in the past for possession of marijuana with intent to distribute. Maybe there was more money there, and the $5,000 was overlooked. Or maybe there was much more pot and it was somebody’s idea of a joke to sprinkle some of it on the victims.

Another theory regarding the unemployed Tamerlan is that he was just looking for what one veteran counterterrorism investigator terms “a little financing.”

As for other possible suspects, one early person of interest in the case was Mess’s girlfriend. She is said to have become so furious with him a week before the killings that she began throwing bottles and even knives. But she had apparently then left town. She is said to have been the woman who discovered the bodies and ran screaming from the apartment.

“There’s blood everywhere!” she was heard to cry out.

And then there was a 19-year-old next-door neighbor, who was arrested 11 days after the killings for allegedly bursting into a shed wearing a mask and brandishing a knife while shouting, “Give me your weed!” He is further alleged to have hopped into a car being driven by a friend and commanded, “Just drive, or I’ll kill you.”

Yet the teen did not seem capable of slitting the throats of three men, especially when they included Mess, a skilled mixed-martial-arts fighter. The case remained unsolved a year and a half later, and it seemed all too apt that the killings had taken place on a dead-end street.

Then came the Boston Marathon bombing and word that Tamerlan was known to have introduced Mess as his best friend. The two are said to have trained together every day at a local boxing gym before “Tam,” as he was known, turned into a kafir-hating fanatic.

With the bombing and the subsequent shootout, Tamerlan proved he was capable of horrific violence, able to kill even children, prepared to execute a cop who was just sitting in a patrol car. Tamerlan further demonstrated that he was so fanatic as to charge straight at the cops during a shootout, tossing explosives and firing and reloading until he had expended his very last bullet, despite being shot multiple times himself.

He clearly had it in him to kill anybody at all in the name of God. Someone who can blithely murder young innocents could certainly murder a friend he might have imagined to be a corrupter.

The guns establish that Tamerlan also had the means to get three men down on the floor and submit to being bound before having their throats cut, a method not unpopular among jihadis.

Who knows, it may even prove to be significant that the two victims other than Mess, Weissman and Raphael “Rafi” Teken, were Jewish.

That is all speculation, but the Middlesex County District Attorney’s office says it is pursuing any leads regarding the killings that may arise from the bombing case.

“The 2011 homicides in Waltham remain an active and ongoing investigation,” a spokeswoman reports.