By Steve Helling
October 06, 2016 02:09 PM
Credit: Florida State University College of Law

A 33-year-old man agreed to plead guilty to the second-degree murder of former Florida State law professor Dan Markel and will provide key information about the 2014 execution-style killing, according to multiple reports.

Luis Rivera, a convicted felon currently serving a 12-year prison sentence for a gang-related conviction, will serve an additional seven years as part of the deal. He had initially pleaded not guilty, but now he admits to obtaining the gun and driving the getaway car used in Markel’s killing. Rivera alleges that a co-defendant, Sigfredo Garcia, shot the popular law professor and blogger execution-style in his Tallahassee home.

But authorities say that Rivera and Garcia did not act alone.

Markel was in the midst to a contentious divorce and custody battle and police believe that his ex-wife’s brother orchestrated the murder. According to a probable cause affidavit filed in September and obtained by PEOPLE, “Investigators believe motive for this murder stemmed from the desperate desire of the Adelson family to relocate Wendi and the children to South Florida, along with the pending court hearing that might have impacted their access to the grandchildren.”

In the affidavit, investigators laid out their theory of the alleged plot: They believe that Charlie Adelson, the brother of Markel’s ex-wife, Wendi Adelson, hired Rivera and Garcia to carry out the murder.

So how did Adelson allegedly connect with Rivera and Garcia?

The affidavit, alleged that Adelson and Garcia had both dated the same woman: Katherine Magbanua, 31, who was arrested Saturday on first degree murder charges. Police allege Magbanua helped orchestrate the killing, alleging Adelson, Magbanua, Rivera and Garcia are “responsible for the murder of Daniel Markel.”

Magbanua allegedly began receiving checks from the Adelson family’s dentistry practice after Markel’s death, the affidavit states. Rivera and Garcia allegedly purchased several cars and motorcycles, according to the affidavits.

The affidavits also allege that Charlie Adelson had previously looked into hiring a hitman.

Despite the allegations in the affidavit, Adelson has not been charged with a crime.

To piece everything together, authorities needed a witness. As part of Rivera’s plea deal, he is expected to turn on his alleged co-conspirators and help with the prosecution.

(Magbanua has not entered a plea and information about her attorney was unavailable Thursday. Rivera has pleaded not guilty. )

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Chief Assistant State Attorney Georgia Cappleman believes that Rivera’s help is an important development in the case and that his cooperation will help them prosecute the other defendants.

“It’s a necessary evil,” Cappleman told “Otherwise, you’re looking at the possibility of other culpable parties not facing any ramifications for their role in the crime.”

In a statement obtained by PEOPLE, Charlie Adelson’s attorney says that Rivera was a desperate man facing life in prison, and his information is not to be trusted.

“The prosecution admittedly didn’t have enough evidence so it went out and bought some by giving away the farm to a murderer. This convicted gangster knows the game and would have said anything not to come out of prison in a box,” attorney David Oscar Markus said in the statement. “Seven years is just offensive. The prosecution literally threatened him with the needle to get this testimony. That’s not a search for the truth. That’s a deal with the devil.”

Garcia faces trial later this month.