BOSTON — Federal prosecutors believe a Boston-area man, arrested this week on drug charges, possessed a handgun the Boston Marathon bombing suspects are thought to have used to kill a university police officer, the man’s lawyer said Thursday.

Stephen Silva, a high school friend of bombing suspect Dzhokhar Tsarnaev, was arrested Tuesday and charged with distributing heroin, as well as possessing a Ruger P95 9mm pistol, which had its serial number filed off in 2013 before the marathon bombing, according to court records.

The Ruger is the same sort of weapon prosecutors contend Tsarnaev and his brother, Tamerlan Tsarnaev, used to kill Massachusetts Institute of Technology police officer Sean Collier on April 18, 2013, three days after the bombing that killed three people and injured more than 260.

Prosecutors have not publicly confirmed that the weapon Silva is charged with possessing was the same one recovered after a gun battle with the Tsarnaev brothers, hours after they are accused of killing Collier.

However, Silva’s attorney Jonathan Shapiro said prosecutors told him they believe it was the same weapon.

It was unclear how prosecutors concluded Silva had the gun before the Collier shooting.

Silva is the fifth friend of the Tsarnaev brothers to face criminal charges. Earlier this week, Kazakh exchange student Azamat Tazhayakov was convicted of obstruction of justice for removing a backpack containing fireworks from Dzhokhar Tsarnaev’s dorm room.

None of the friends has been charged with a role in the bombing attack.

Dzhokhar Tsarnaev is awaiting trial on charges that carry the death penalty. Tamerlan died following a gunfight with police hours after prosecutors believe the pair shot Collier.