Yesterday, victims of the Boston Marathon bombings watched in a federal courtroom as Dzhokhar Tsarnaev pleaded not guilty to 30 charges.

Dzhokhar and his brother Tamerlan, who died during a police shootout, are accused of setting off explosives that killed three people and injured 260 more. And some are wondering if those deaths could have been prevented with some police work in 2011.

Back then, investigators discovered a grisly crime scene in a Boston suburb. Three men, their throats slashed open, laid dead in the exact same position, with seven pounds of marijuana dumped over their bodies.

In May, the public learned that Tamerlan could have been involved in the killings when an acquaintance of his, Ibragim Todashev, confessed to the triple-homicide before being shot to death by the FBI during questioning.

Until recently, the narrative has been that the police were stumped in 2011 and only now are uncovering the possible connection with Tamerlan. A new investigation by The New York Times, however, suggests that police were given information about him after the triple-murder but never took him in for questioning.

Tamerlan was reportedly a close friend of one of the victims, Brendan Mess, and repeatedly visited the apartment where the bodies were found, according to the Times. A friend of Mess says he told police about the victim's friendship with Tamerlan several times, including after the alleged Boston bombing suspect didn't show up to the funeral.

The story also claims that police failed to show up to a mixed martial arts gym where Mess and Tamerlan reportedly worked out together. If they had, they would have met the owner of the gym, John Allan, who recounted to the Times how Tamerlan reacted to the killings in 2011:

As I said something, there was kind of a smile on Tamerlan's face, and he laughed it off. He laughed off the fact that he was murdered, like: "Aw, man. It's crazy right? Huh huh. It's crazy right?" That really shocked me. [New York Times]

The mother of another one of the victims, Eric Weissman, claimed that the police seemed "passive and waiting" and told her that in the future they expected "someone with information might come forward and admit it and seek a plea deal."

Police originally deducted that the crime was carried out by "professionals" who knew the victims and were probably involved with the drug trade. They also had allegedly been told about Tamerlan, a mixed martial arts fighter who was friends with Mess and was believed to have dealt marijuana. So why didn't they ever question him?

One law enforcement official told the Times that despite the evidence now mounting against Tamerlan, they really didn't know much about the connection back then: "Don't you think if someone had told us to take a look at him and that he had information, we would have talked to him?”