Josh Duhamel thinks he knows the secrets behind Tupac Shakur's murder.

The 45-year-old actor has grown increasingly familiar with the circumstances surrounding the shootings of Tupac in 1996 and his rap rival The Notorious B.I.G in 1997 since being cast in 'Unsolved: The Murders of Tupac and The Notorious B.I.G', and he's convinced he knows who is responsible for Tupac's death.

Josh - who portrays Detective Greg Kading in the 10-part series - explained: ''The show is called 'Unsolved', but we all know what happened. And that's one thing that I think people are going to be most surprised by.

''We have a very good idea - whether we agree that the police were involved - there were definitely some shady things that were going on. Did they do it? Did they not do it?''

Tupac was killed in a drive-by shooting in Las Vegas after attending a Mike Tyson boxing match at the MGM Grand casino earlier in the night.

Since his death, there have been numerous theories as to who killed him, but no one has been charged with the murder.

Josh explained that although he claims to know what happened on the night of Tupac's death, it's very difficult for anyone to prove.

Speaking to Us Weekly, he said: ''It's not what you know, it's what you can prove, and that's the tragedy of this story. There's so many conflicting theories that it's hard to sift through it all and find out what the actual truth is.''

Josh also claimed that Tupac's impact can still be seen in how his fans continue to speculate about his death.

He explained: ''One can only hope to have people speculate on whether or not he's still alive or not. I wish people do that about me, but they won't. Tupac Shakur was larger than life.''