Jesse Matthew Jr. was convicted of the murders of college students Hannah Graham and Morgan Harrington. (Steve Helber/AP)

The family of the man convicted of killing University of Virginia student Hannah Graham pleaded with him to work with police to help find her in the days after she went missing in the fall of 2014, according to a newly unsealed arrest warrant.

Jesse Matthew Jr.’s aunt, Alice Fletcher, said she told him that her family was going to do everything it could to help Graham’s family find the missing 18-year-old from Fairfax County.

Fletcher said she told Matthew, 33, of Charlottesville, that he needed “to go home and clear his head and think about what happened to the victim because she is someone’s child,” according to the court document.

The warrant also says that Matthew’s mother told him they were going to get together as a family and get Matthew to “do what he needs to do” to help with the case, but Matthew disappeared, touching off a national manhunt that led to his capture on a Texas beach.

The information is contained in an arrest warrant filed by an FBI agent in federal court in Virginia. It provides the first look at how Matthew’s family handled authorities’ growing suspicions that Matthew killed Graham. The warrant was first reported by WTOP.

Matthew pleaded guilty this month to killing Graham and Virginia Tech student Morgan Harrington, who disappeared in 2009, as part of a deal with prosecutors that spared him the possibility of the death penalty in Graham’s case. He was serving a life sentence for a brutal sexual assault in Fairfax City in 2005 and received additional life sentences as part of the plea deal.

Graham disappeared Sept. 13, 2014. The arrest warrant covers the actions of Matthew’s family members a little more than a week later, after Charlottesville police had homed in on Matthew as a suspect in Graham’s disappearance, interviewed him and gotten a search warrant to examine his car.

Graham had spent a night out in Charlottesville when she disappeared. Matthew, who did not know her, met her on the street and later abducted her. Her body was discovered outside of Charlottesville.

The arrest warrant also offers new details about the manhunt for Matthew. The documents reveal that license-plate readers in Louisiana scanned the plates of the car Matthew was driving, and cellphone records show that he placed a call from the state before he was captured.