According to an FBI agent, the family of Jesse Matthew pleaded with him to help find Hannah Graham during the period police believed she was still alive.

WASHINGTON — Family members of Jesse Matthew pleaded with him to help find Hannah Graham during the time police believed the University of Virginia student was still alive, “because she is someone’s child.”

In a newly unsealed document dated Sept. 22, 2014, FBI special agent Robinson Blake detailed some of the evidence police had gathered against Matthew as they searched for Graham, who was last seen with Matthew in the early morning hours of Sept. 13, 2014.

In addition, the document provides new insight into efforts by Matthew’s family to have the then-32-year-old Charlottesville man cooperate with police in their search for Graham.

Three days after Charlottesville police had seized Matthew’s car and searched his apartment, Matthew’s aunt, Alice Fletcher, told a Charlottesville detective that she and her family were trying to do everything they could to help the Graham family, and that if Matthew had anything to do with the sophomore’s disappearance, they intended to do the right thing.

In the affidavit in support of an arrest warrant for unlawful flight to avoid prosecution, filed in federal court, the FBI agent said Fletcher had tried to impress upon Matthew the importance of cooperating with police.

According to the agent, Fletcher told Matthew that she “needed him to go home and clear his head and think about what happened to the victim because she (Hannah Graham) is someone’s child.”

Blake said Fletcher told Matthew he “needed to think because the Police are going to come back and they need to know what he knows so they can have a chance to find the victim,” according to the document, which was unsealed after Matthew pleaded guilty earlier this month to the 2014 murder of Graham and the 2009 murder of Virginia Tech student Morgan Harrington.

Fletcher told Blake that Matthew’s mother, Debra Carr, had told her son that “they were getting together as a family because they needed to address this and get him to do what he needs to do.”

However, the morning the family was set to meet, Carr woke up and found that her son was gone.

License plate readers in Louisiana captured a Nissan Sentra belonging to Matthew’s sister on Sept. 21 and Sept. 22.

The next day, Matthew’s father got a cellphone call from his son in Louisiana, on another person’s phone, according to call records that include the location of cellphone towers.

On Sept. 23, as Charlottesville police searched for Matthew, he was charged with abduction with intent to defile in Graham’s disappearance.

The following day, Matthew was spotted and arrested in Galveston, Texas.

Graham’s remains were found behind an uninhabited home in Albemarle County, Virginia. An autopsy determined she was slain.

After Matthew’s guilty plea in the Graham and Harrington murders, a statement of facts stipulated to by both his defense team and prosecutors show that police believe Matthew murdered Graham in the early-morning hours after leaving the Charlottesville downtown mall.

Matthew is serving seven life sentences for the murders of Graham and Harrington, and the attempted 2005 murder of a woman in the City of Fairfax.

Matthew’s current and former attorneys did not respond to requests for comment on the newly unsealed document.