Police in Massachusetts are re-examining a brutal 2011 triple murder involving the best friend of the now-dead suspect in the Boston Marathon bombings.
Authorities have confirmed they are investigating a possible link between Tamerlan Tsarnaev, 26, killed during a gun battle with police on Friday, and the murder of a man said to be his close friend, Brendan Mess, 25. Also killed were Erik Weissman, 31, and Raphael Teken, 37.
The bodies of the men were discovered in September 2011 at Mess's home in the Boston suburb of Waltham. Each of the men's throats were slashed and they were almost decapitated. Their mutilated bodies were covered with marijuana.
"We are looking at a possible connection with the suspect in the marathon atrocity and this active and open homicide in Waltham," Stephanie Guyotte, a spokeswoman for the Middlesex County District Attorney, told American ABC.
But another spokeswoman for the office, MaryBeth Long, told The Associated Press that it was "customary" to examine new crimes and unsolved crimes to look for links between them.
ABC quoted two unnamed law-enforcement sources as saying that the lack of leads in the murder cases may change, with the focus now turning to Tsarnaev.
Investigators initially said the victims were targeted, but had no clear motive.
Describing the murders as "the worst bloodbath I have ever seen in a long law-enforcement career", another unnamed local police source said the bombings proved Tsarnaev was capable of violence.
"There was no forced entry, it was clear that the victims had let the killer in," the unnamed source said. "And their throats were slashed right out of an al-Qaeda training video. The drugs and money on the bodies was very strange."
It was also reported that Tsarnaev was arrested in July 2009 on charges of beating his then-girlfriend. The case was dismissed, ABC reported.
Mr Mess's relatives were reported to have told police that it was "odd" Tsarnaev did not attend Mr Mess's funeral.
Former friends and associates of Tsarnaev have said they thought he could be connected to the murders.
One, identified only as Ray, told US website BuzzFeed that it was strange Tsarnaev said he did not have any American friends.
"Tam wasn't there at the memorial service, he wasn't at the funeral, he wasn't around at all," Ray said.
"And he was really close with Brendan. That's why it's so weird when he said 'I don't have any American friends'.
"He was somebody who was in contact with Brendan on a daily basis. Anybody like that you would think they would have been around."