Did Boston bombing suspect Tamerlan Tsarnaev steal the gun used to kill police officer Sean Collier

The Globe reported today that the gun used by the Tsarnaev brothers during the Watertown shootout may have been stolen from a Waltham murder victim.

Middlesex District Attorney Marian T. Ryan issued a statement today defending the pace of the investigation, a statement that also made clear Ryan’s office believes it is constrained by ethics rules for lawyers from publicly discussing an ongoing investigation.

“While we can not discuss details pertaining to the investigation, including evidence, suspects or witnesses, this office and its law enforcement partners have conducted a thorough, far-reaching investigation beginning in 2011 when this horrific crime occurred,’’ Ryan said in the statement. “This investigation has not concluded and is by no means closed.”

The statement did acknowledge that the FBI is now part of the investigatory team, which also includes prosecutors and Waltham and State Police. The FBI does not routinely participate in murder investigations in Massachusetts.

Ryan said her office would not discuss the investigation with the public. ....

The current Moscow-backed leadership of Chechnya has been ruthless in prosecuting suspected separatists. But Abdulbaki Todashev, who is a department head in the mayor’s office in Grozny, the capital of Chechnya, said his son had no reason to fear repression or persecution in Chechnya.

“He was too young to fight in the war, and he has nothing to fear here now,” Abdulbaki Todashev said. “He would have faced no oppression here.”

Todashev said he moved his family out of Chechnya to Saratov province in central Russia during the worst of the fighting, and moved them back “five or six years ago.” Ibragim was studying English at Chechnya State University when he told his father in 2008 he wanted to study in the United States.

“He was a good student, he really loved English, and he went to the US for English practice,” the father said. He said that Ibragim had not been accepted into any formalized course of study, and understood that he was on an exchange program.

....It was not certain who, or how many officers, had fired on Mr. Todashev. Nor was it clear why, with at least three law enforcement officials in the room, deadly force was used on someone without a firearm in his hands. Asked, one law enforcement official said: “If somebody jumps on you and you have a gun, and you don’t do something, the gun will quickly come into play.” ....

There was no indication on Wednesday why Mr. Todashev — who, like the Tsarnaevs, was an ethnic Chechen — would have implicated himself and Mr. Tsarnaev in the murders. Investigators, who are seeking to determine how Mr. Tsarnaev made money, have been looking into whether Mr. Todashev and Mr. Tsarnaev were drug dealers, one of the law enforcement officials said.

Mr. Todashev had not signed a written statement about the Waltham murders before he was fatally shot. “He had only said it orally but had not signed anything,” said the first official. “But that was where it appeared to be heading.”