On Monday afternoon, the Kaufman County Sheriff's Department released the probable cause affidavit outlining the terroristic threat charges against Eric Williams.
In the affidavit, officials said law enforcement officials in Kaufman County received a threat on March 31 that said "unless law enforcement responded to the demands of the writer, another attack would occur."
Police said investigators determined the author of the email possessed "unique identifiers to send the electronic communication." The affidavit went on to say the following:
"A search warrant was executed on April 12, 2013 at the residence of defendant, Eric Lyle Williams at 1600 Overlook Drive, Kaufman, Kaufman County, Texas. During the search of the residence, it was learned that the defendant had utilized these unique identifiers to send the threat via the electronic communication from his personal computer."
The probable cause affidavit was followed by an arrest warrant for Williams for terroristic threat.
The electronic threat was received March 31, one day after the murders of District Attorney Mike McLelland and his wife Cynthia.
Officials in Kaufman County have not yet released the search warrants related to Williams, but expect those to be released soon.
"All search warrant affidavits are sealed by court order. The actual warrants will be available once filed with the courts. Once filed, they will be distributed as well," said Lt. Justin Lewis, of the Kaufman County Sheriff's Office, via email.
A member of the family spoke with NBC 5 Monday afternoon after speaking with authorities says it "looked it a bomb went off in the house" after authorities took computers and file boxes from Williams' home.
On Saturday night, agents searched a storage facility in Seagoville and towed away a white Crown Victoria and there were more than 20 guns recovered from that unit. So far, investigators haven't revealed any connection between Williams and the storage unit or car.
NBC 5's Ray Villeda contributed to this report.