Tupac Shakur. (AP)

Chat with Fred Johnson, co-author of “Tupac Shakur: The Life and Times of an American Icon,” today at noon.

A prisoner has supposedly confessed to being involved in the 1994 robbery of Tupac Shakur, in a statement posted online Wednesday, the eve of what would have been the rapper’s 40th birthday.

In a confession posted on AllHipHop.com, Dexter Isaac, who is serving a life sentence on unrelated charges, said he was paid $2,500 by James Rosemond to rob the rapper outside Quad Studio in New York. Shakur was shot during the robbery, but Isaac does not identify the shooter in the statement.

The attack fueled the East-West coast conflict already brewing between Shakur and Christopher “The Notorious B.I.G.” Wallace. Shakur and Wallace were killed in 1996 and 1997, respectively, and the crimes are still unsolved.

New York police said they will investigate the inmate’s claim.

Isaac’s supposed confession is addressed to Rosemond, a rap manager, also known as Jimmy Henchman, who is currently being sought by federal authorities for his alleged involvement in a drug trafficking ring.

MTV points out that before his death Shakur suspected Rosemond was involved in the crime. In the song “Against All Odds,” Tupac raps, “And did I mention, promised a pay back, Jimmy Henchman, in due time/ I know you [expletive] is listenin’. The world is mine. / Set me up, wet me up, [expletive] stuck me up. / Heard the guns bust, but you tricks never shut me up.”

Rosemond’s lawyer, Jeffrey Lichtman, responded to Isaac’s allegations in a statement to the New York Post: “He’s a convicted killer who was brought back by the U.S. Attorney, solely to cooperate against Jimmy Rosemond, and wouldn’t you know it, he spins this tale.”

"I want to apologize to [Shakur’s] family and for the mistake I did for that sucker [Rosemond],” Isaac told AllHipHop.com. “I am trying to clean it up to give [Shakur and Wallace’s] mothers some closure.”

Related coverage:

The Root: Tupac at 40

Chat: Author Fred Johnson talks Tupac

Read the full confession below: