The 2014 murder of Florida State University law professor  likely stemmed from his ex-wife's family's desire to pave the way for her to move away and take the couple's two young children after a "bitter divorce" with still-unresolved custody issues, investigators allege in a newly released court document obtained by PEOPLE.  The probable cause affidavit lays out the allegations that led to the May 25  of Sigfredo Garcia, 34, of Miami Beach, which suggested an answer to the long mystery of who shot the popular and nationally respected professor execution-style as he sat in his Honda Accord in the garage of his suburban Tallahassee home on July 18, 2014.  Markel's wife, Wendi Adelson, had been a member of the Florida State University law school faculty along with her ex-husband. She filed for divorce in September 2012, the divorce was granted in July 2013, and she formally resigned from her post in January 2015. She currently lives in South Florida.  Markel was killed ahead of an unscheduled court hearing where he planned to ask the court to limit their children's contact with Adelson's mother, Donna, whom he claimed had "made disparaging remarks about him to his sons," the affidavit states.  "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," according to the document.  Although only Garcia has been charged – he pleaded not guilty Thursday – the document alleges that he and another man, Luis Rivera, murdered Markel.  Rivera, 33, is currently in a federal prison in Florida on unrelated charges, said Tallahassee Police Chief Michael DeLeo in a news conference Thursday. Charges against Rivera in the Markel case are forthcoming, he said.  He added that it's "more probable than not" there will be additional arrests. He did not address whether any of the Adelsons are suspects, nor whether he knows their current whereabouts. "We aren't on speaking terms," he said.  Garcia and Rivera match descriptions of suspects seen in the area at the time of the murder, their movements place them in Tallahassee on that day, and they had rented a silver Pine Mica Toyota Prius for their travel from South Florida, which further matched descriptions of a vehicle seen leaving the area after the shooting.  The document further states that around the time of the murder, Wendi Adelson's brother Charlie "was involved in a personal relationship" with the mother of Garcia's children, Katherine Magbanua, who was also listed as a business associate of Garcia's.  Prosecutors would not comment on whether Charlie or Wendi Adelson are being considered as suspects,  Authorities tied Garcia and Rivera to the case using cell phone data, ATM transaction records and a Tallahassee eyewitness, who met with Garcia and Rivera a month or more before the murder, according to the affidavit. The eyewitness was asked, and agreed, to rent a motel room in the witness's name for Garcia and Rivera on the night preceding the murder. The witness also recalled Rivera having in his possession "a silver finish, short-barrel revolver handgun" at the time they met.  "Recovered evidence from the crime scene indicates the caliber of firearm used in this murder is consistent with revolver ammunition and no spent casing was found at the scene," according to the affidavit. "This investigation did not reveal any other legitimate purpose for either suspect to be in Tallahassee at the time of the murder."  The document describes a contentious relationship between Markel and his ex-wife's family.  Wendi filed for divorce on Monday, Sept. 10, 2012, it states. "Markel reportedly returned home from a business trip to find his family gone, a majority of the contents of the house missing and the paperwork for dissolution of marriage displayed on his bed," it says. After learning she and the children had relocated to her parents' home in South Florida, he "protested" and she returned to Tallahassee with the childen "until legal arguments could be heard."  In June 2013 a judge denied Wendi's motion to relocate with the children.  "Email evidence indicates Wendi's parents, especially her mother, wanted Wendi to coerce Markel into allowing the relocation to South Florida. Additionally, Wendi's brother Charles reportedly did not like Markel and did not get along with him," the document reads.  In March 2014, Markel filed a motion regarding provisions of the divorce settlement agreement. "One of the points of contention in this motion was Wendi's mother, Donna Adelson, and her reported negative interaction with the children," according to the document. "Markel claimed Donna made disparaging remarks about him to his sons."  "Markel sought relief in this motion by asking the court to prohibit Donna from having unsupervised time with her grandchildren and to impose limitations to prevent the children from being subjected to disparaging comments about their father," it states.  The motion was scheduled to be heard in court, but the hearing was delayed and had not yet been rescheduled at the time Markel was killed.
Dan Markel was shot in his driveway in 2014 ahead of a hearing tied to child custody issues