BOSTON (AP) -- Details emerged Wednesday on another friend of Boston Marathon bombing suspect Dzhokhar Tsarnaev who may have been linked to events surrounding the deadly attack, this one a high school classmate tied to a gun used to kill a university policeman during a manhunt for Tsarnaev and his brother.
Stephen Silva, who also enrolled at the same university as Tsarnaev, was arrested this week on federal charges of heroin trafficking and possession of a handgun with an obliterated serial number. The gun was used to kill Massachusetts Institute of Technology police Officer Sean Collier while the Tsarnaevs were being sought, according to two people with knowledge of the case who spoke to The Associated Press on the condition of anonymity because they weren't authorized to discuss the investigation.
Silva told police he smoked marijuana every day because "my best friend was the bomber," according to court documents in a state case from last year.
Silva was a close friend of Tsarnaev, who's accused with his brother, Tamerlan Tsarnaev, of setting off bombs at the April 2013 marathon, killing three people and injuring more than 260 others, and then ambushing Collier days later and shooting him multiple times in his car. He's one of five men connected to the Tsarnaevs who have been charged in the bombing investigation.
On Monday, the day Silva was arrested, a federal jury found Azamat Tazhayakov guilty of obstruction of justice and conspiracy for trying to protect Dzhokhar Tsarnaev by agreeing with another friend, Dias Kadyrbayev, to get rid of a backpack and disable fireworks they took from his dorm room. Kadyrbayev is to be tried next month on the same charges.
Robel Phillipos, who is charged with lying to investigators about being in the dorm room with Kadyrbayev and Tazhayakov the night the items were taken, is to have a separate trial in September. And Khairulluzon Matanov is to be tried next year on charges that he lied to investigators about the extent of his friendship with Tamerlan Tsarnaev and the contact he had with both brothers after the bombings.
Silva was arrested on marijuana charges at a train station in the Dorchester neighborhood in November. After transit police found two bags of marijuana and a wad of $555 in cash in his pockets, he repeatedly told them, "I smoke a lot of weed every day because my best friend was the bomber," court documents say.
George Hinson, who attended the Cambridge Rindge and Latin school with Silva, Silva's twin brother and Dzhokhar Tsarnaev, said Silva's arrest came as a shock.
"He would not have given (Tsarnaev) the gun or hidden it if he knew he was a terrorist," Hinson said. "Tsarnaev probably gave him a different story. He probably just wanted to make sure his friend was protected."
Hinson said Silva and his twin brother, Steven Silva, initially enrolled at the University of Massachusetts-Dartmouth, where Tsarnaev went, but the twins eventually transferred to the UMass campus in Boston.
"Steven was the pretty boy," Hinson said. "Stephen was sort of the laid-back one."
Cordelia van Heeckeren, who lives on the floor of the Cambridge high-rise apartment building where the Silva twins lived with their parents, said she was stunned when she saw FBI agents with hacksaws preparing to enter the Silvas' apartment Monday. She said the twins seemed to have a regular group of friends and were generally well-behaved.
Attorney Jonathan Shapiro, who represents Stephen (pronounced STEF'-an) Silva in the federal case, said Wednesday he couldn't elaborate on his earlier statement that he was still meeting with his client and reviewing the case.
"According to news reports, law enforcement officials say it is the same weapon that was used ... in the MIT officer Sean Collier shooting," Shapiro said Tuesday, after Silva made his initial court appearance. "However, this has not been charged in the indictment."
The state court documents didn't explain whether Silva believed his friend Tsarnaev was the bomber because of news reports identifying the Tsarnaevs as the suspects or through other means. They also didn't elaborate on why he said he smoked marijuana because of what he believed was his friend's role in the deadly bombing.
According to the federal indictment, Silva received the gun in or around February 2013. It said the gun "had the importer's and manufacturer's serial number removed, obliterated, and altered and had previously been shipped and transported in interstate and foreign commerce."
The gun was recovered in suburban Watertown, where authorities say the Tsarnaevs shot at police and threw pipe bombs at them during the manhunt. Watertown police have said Tamerlan Tsarnaev fired the gun at them and then threw it at them when it ran out of bullets.