BOSTON — A college friend of Boston Marathon bomber Dzhokhar Tsarnaev was sentenced Tuesday to six years in prison after he apologized to the victims and their families for not calling police when he recognized photos of Tsarnaev as a suspect.

Dias Kadyrbayev, 21, pleaded guilty last year to obstruction of justice and conspiracy charges for removing items from Tsarnaev’s dorm room after recognizing his friend in photos released by the FBI days after the bombing.

Prosecutors say Kadyrbayev exchanged text messages with Tsarnaev, then went to his room with two other friends. There, he and another man agreed to remove Tsarnaev’s computer and a backpack containing fireworks that had been partially emptied of their explosive powder. Kadyrbayev also threw the backpack into a garbage dumpster.

Kadyrbayev said Tuesday that he had no explanation for his actions.

“I can’t find an answer. I really can’t believe that I acted so stupidly,” he told Judge Douglas Woodlock before his sentence was imposed.

Kadyrbayev had faced up to seven years in prison. His lawyer had sought a three-year sentence.

He will get credit for the 26 months he’s been in custody and will be deported to his native Kazakhstan when his prison term is up.

In sentencing memos filed in court, prosecutors said Kadyrbayev had the power to help law enforcement identify Tsarnaev and prevent additional violence, possibly including the murder of Massachusetts Institute of Technology police Officer Sean Collier, who was killed by the Tsarnaev brothers as they tried to flee after the FBI released their photos. Dzhokhar’s older brother, Tamerlan, died after a shootout with police.

“Hours before (Dzhokhar) Tsarnaev murdered Officer Collier, the defendant (Kadyrbayev) recognized that his friend Tsarnaev was the fugitive bomber. Any reasonable, decent person possessed of the information the defendant had would have recognized that immediate apprehension of Tsarnaev was a public-safety imperative,” prosecutors wrote.

Collier’s sister had been expected to speak Tuesday, but at the beginning of the hearing, prosecutors informed the judge that she had decided not to. A prosecutor did, however, quote from a letter written by Collier’s stepfather in which the family said they believe if Kadyrbayev had reported Tsarnaev’s identity to authorities, he could possibly have prevented Collier’s death.

Kadyrbayev’s father, Murat, traveled from Kazakhstan to attend his son’s sentencing hearing. He said his son didn’t fully understand in the moment how serious his actions were.

“Had he known what he was doing and had he understood what he was doing, we wouldn’t be standing here,” Murat Kadyrbayev said through a translator outside court.

Three people were killed and more than 260 were injured in the bombing April 15, 2013, near the marathon’s finish line. Tsarnaev was sentenced to death for the attacks.