Lawyers for Abdulbaki Todashev, the father of the witness in the Boston Marathon bombing, Ibragim Todashev, who was fatally shot by a Federal Bureau of Investigation (FBI) agent in May, have announced the launching of an investigation into the circumstances surrounding the killing.

Ibragim Todashev, 27, an ethnic Chechen and friend of Boston Marathon bombing suspect Tamerlan Tsarnaev, was killed while being interrogated by FBI agents in his Orlando, Florida home in connection with the April 15 bombings that killed three people and injured more than 260 others.

No one has been charged in the execution-style killing. The name of the FBI agent who shot the young Todashev, multiple times and at close range, according to press reports, has not even been released. The FBI, an arm of the Obama administration Justice Department, has blocked the release of an autopsy of the young man, and Florida authorities have rejected calls for an independent state investigation.

The mass media have imposed a virtual blackout on the Todashev killing, and largely ignored the announcement of a private investigation by Abdulbaki Todashev.

The elder Todashev spoke at a press conference Tuesday in Tampa, Florida, explaining that lawyers appointed by the Council for American-Islamic Relations (CAIR) had hired private homicide investigators to ascertain the circumstances surrounding the May 22 death of his son.

“I want justice, honestly, because an unprecedented, intentional murder of my son took place,” Abdulbaki said in a related interview with Russia Today. The lawyers announced that once the investigation had been completed they would consider filing a lawsuit against the US government.

Todashev also plans to meet with Jeffrey Ashton, the state attorney for Orange and Osceola counties in Florida, which include the city of Orlando. Ashton has agreed to review the case.

Abdulbaki Todashev’s lawyers said the FBI had sent agents to monitor the press conference and arrange to question Todashev, which he refused. “We’re not going to talk to them, with a lawyer, without a lawyer,” said Barry Cohen, head of the legal team representing Todashev.

Refuting claims by the FBI that Ibragim Todashev, who was unarmed, had initiated a violent confrontation that led to his death, lawyers from CAIR revealed that at the time of the killing, the younger Todashev was disabled due to recent knee surgery.

The lawyers further argued that if the FBI agents interrogating Todashev had felt their lives to be threatened, they all would have responded by drawing their weapons and firing on the alleged attacker. But, as inquiries by former detectives hired by CAIR had ascertained, all the bullets were fired from the gun of a single unnamed FBI agent.

In response to the press conference, FBI officials released a statement reasserting their claim that the witness initiated a “violent confrontation” to which the FBI agents responded appropriately.

The state murder of Ibragim Todashev is only one of many aspects of the Boston Marathon bombings that remain unexplained. The government has acknowledged that both the FBI and the CIA had been warned by Russian authorities of Tamerlan Tsarnaev’s extreme Islamist sympathies and links to separatist and terrorist groups in the North Caucasus, which includes Chechnya and Dagestan. The FBI says it investigated the older Tsarnaev brother in 2011, but concluded there was nothing suspicious about him and ended the probe.

Nevertheless, Tamerlan Tsarnaev was placed on at least two terrorist watch lists. That, however, did not prevent him from traveling unimpeded to Dagestan in 2012, where he stayed for six months and reportedly made contact with Islamist separatist insurgents.

Finally, according to both the FBI and Massachusetts state and local police officials, the federal agency never informed its local counterparts in a Joint Terrorist Task Force about its knowledge of Tamerlan Tsarnaev in the run-up to the Boston Marathon, a major national and international event attended by many thousands of people.

Todashev, an ethnic Chechen, may have had compromising information about links between the Tsarnaevs and US intelligence agencies.

Also on Tuesday, former classmates of Dzhokhar Tsarnaev, the younger suspect in the Boston bombings, were arraigned in Federal court on charges of removing evidence from their friend’s dorm room in the aftermath of the bombings. Kazakh nationals Dias Kadyrbayev and Azamat Tazhayakov face the possibility of deportation or more than 20 years in prison if they are found guilty of altering evidence connecting the younger Tsarnaev to the April 15 events. The two defendants pleaded not guilty.