Warning: Details in this report contain graphic content.

FIRST ON FOX: Alex Murdaugh's youngest son Paul sent his friends a Snapchat video shortly before his murder — and it is a key piece of evidence in the state's case against him, South Carolina prosecutors revealed Wednesday in a new court filing.

The disbarred attorney, 54, is slated to go to trial Monday for the double slaying of Paul, 22, and Murdaugh's wife, Maggie, 52, in June 2021. 

"Amongst other things, critical to the case is a video sent out to several friends at approximately 7:56 p.m. on the night of the murders," wrote Senior Assistant Deputy Attorney General Creighton Waters in a petition to secure the attendance of a Snapchat witness. "The contents of this video is important to proving the State's case in chief."

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Murdaugh family posing in front of a tractor.

From left, Buster Murdaugh, his mother Maggie, his brother Paul and his father Alex. Alex is accused of fatally shooting Maggie and Paul on June 7, 2021. (Facebook)

It's the first time the video has been mentioned publicly by prosecutors, who have been tightlipped about the evidence they have against the scion of the once-powerful legal dynasty. 

In the filing, the prosecutor asked Judge Clifton Newman to sign an order requiring a Snapchat representative to testify at the Colleton County trial.

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"The witness, Snapchat Inc Custodian of Records, of Santa Monica, California, is a material witness because in a search warrant return, Snapchat provided records belonging to one of the victims in this case," Waters wrote in the petition. "Because this video was provided by Snapchat, a Snapchat custodian is required to testify in person that the video is a true and accurate record kept in the normal course of business activity."

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The judge signed the order requiring the Snapchat representative's attendance from the start of the trial "until the witness testifies or the case is disposed of."

The documents do not indicate what is shown on the Snapchat video.

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Murdaugh is accused of gunning down his troubled son and his wife on June 7, 2021, near the dog kennels on their sprawling 1700-acre hunting estate known as Moselle in Islandton, South Carolina. 

Prosecutors say the disgraced attorney used a shotgun to blow off his son's head, which was "severed" from his body, according to court papers.

Diagram part of the Murdaugh trial exhibits

A diagram shows where Paul and Maggie Murdaugh were fatally shot on the family's sprawling hunting estate in Islandton, South Carolina, on June 7, 2021. (Colleton County Court)

Maggie was shot with a semiautomatic rifle five times — including in the back of the head — and died about 30 yards from her son, court papers allege.

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Prosecutors have suggested that the family patriarch murdered Paul and Maggie over mounting debts and fear that his decadeslong schemes to embezzle money from his clients would be exposed.

Murdaugh alleges that he found his wife and son's lifeless bodies at 10:06 p.m. when he placed a hysterical 911 call to police.

Photo from Alex Mudraugh crime scene from trial exhibits

A crime scene photo shows what appears to be blood droplets on the floor, a mannequin and an evidence marker in the feed room where Paul Murdaugh was fatally shot. (Colleton County Court)

More than an hour earlier, a video recorded at 8:44 p.m. shows Paul with his father and his mother, prosecutors previously disclosed. The footage was retrieved from the slain son's phone.

Prosecutors said the victims were killed between 8:44 p.m. and 10:06 p.m., while the South Carolina Law Enforcement Division previously provided a narrower window of 9 p.m. to 9:30 p.m. 

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A spokesman for the South Carolina Attorney General's Office declined to comment on the Snapchat video.

"We can't comment on anything other than what we say in court or in our court filings," said Robert Kittle told Fox News Digital.