Official: Gun Shows Dzhokhar Tsarnaev Played Greater Role in Bombing and Aftermath

BOSTON— -- The handgun used by one of the alleged Boston Marathon bombers in a violent firefight with police and to allegedly murder an MIT police officer was given to the Tsarnaev brothers by a local alleged heroin dealer who was taken into custody late Monday, several law enforcement sources told ABC News.

Stephen Silva, a Cambridge Rindge and Latin classmate of accused Boston Marathon bomber Dzhokhar Tsarnaev, appeared in federal court today on drug and gun possession charges. In addition to charges related to alleged heroin dealing, the Eritrea native “knowingly received and possessed a firearm…a Ruger model P95 9 mm pistol, which had the importer’s and manufacturer’s serial number removed, obliterated, and altered,” according to court documents obtained by ABC News. Silva is alleged to have had the gun in February 2013, just months before the marathon blasts.

Law enforcement sources said that gun was the same as the Ruger P95 described in other court documents as used by Tamerlan Tsarneav, Dzhokhar’s older brother, in a gun battle with police three days after the marathon bombing in April 2013. Tamerlan emptied the gun when firing at police and then threw the empty weapon at the officers before he was killed, the documents say. Dzhokhar was injured, but survived the firefight and would be apprehended hours later. He has pleaded not guilty to a litany of charges related to the marathon bombing.

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Hours before the police engaged the brothers, the same gun was also allegedly used in the murder of MIT security officer Sean Collier.

Defense attorneys for Dzhokhar have filed papers and have said in open court that Tamerlan was the architect of the marathon attacks that left three dead, 260 wounded, and that Dzhokhar came under the “stronger influence of his older brother.”

However, a high-ranking law enforcement official said that while Tamerlan may have used the Ruger last, it was Dzhokhar who was friends with Silva and in the end, “it was Dzhokhar’s gun.”

“The defense is trying to paint Tamerlan as the mastermind [of the Boston attacks], but they were working in concert and we have evidence that Dzhokhar secured the weapon,” the official said.

Though the serial number was damaged, the Bureau of Alcohol, Tobacco, Firearms and Explosives was able to use what was left to track it to a gun to a store in Maine where it had been purchased legally, law enforcement sources said. The original buyer told investigators he gave it to a Portland, Maine drug dealing gang. The alleged leader of that gang has been identified in federal court records as Biniam “Icy” Tsegai, also from Eritrea. Tsegai and others were indicted by federal prosecutors in Maine last year and in recent weeks several of those charged with drug-related crimes have pleaded guilty or been sentenced, according to FBI releases and court records.

It is unclear what connection “Icy” or his associates may have had with Silva or the Tsarnaevs. But Silva was described by investigators as a longtime friend of the younger Tsarnaev – who today turned 21 in jail where he is awaiting trial. Silva told U.S. Magistrate Court Justice Marianne Bowler today that he attended Cambridge Rindge and Latin, the same school as Dzohokhar, and graduated in the same year, 2011.

Silva's attorney, Jonathon Shapiro, issued this statement to ABC News: "I am in the process of meeting with my client and reviewing the available evidence, which will eventually be presented in a court of law in accordance with our system of justice."

Silva will return to federal court next month for a bail hearing.

The FBI has doggedly built cases against four other Tsarnaev friends.

Another Cambridge Rindge and Latin classmate, Robel Phillipos, will go on trial this fall for lying to federal agents.

Yesterday Azmat Tazhayakov, who was with Tsarnaev every day after the bombings, according to court testimony in his trial, was found guilty of obstruction charges and faces twenty years in prison. The FBI dug through a dump for ten days to recover a backpack with spent fireworks Tazhayakov and his roommate are accused of disposing of the night of Collier's murder. That man, Dias Kadrybayev, was also charged with obstruction and is slated for trial this fall. He has pleaded not guilty. Khairullazon Matanov was charged with obstructing justice after he deleted, among other things, a picture of him standing alongside Tamerlan Tsarneav in front of a black flag often associated with jihad, according to FBI report obtained by ABC News. Matanov bought the brothers dinner the night of the attack, prosecutors said.

Michele McPhee is a Boston-based freelance reporter and frequent contributor to ABC News.