Texas authorities have arrested the wife of a disgraced local justice of the peace in connection to the slaying of a district attorney and his wife.

Kim Lene Williams, 46, was taken in custody and held on $3 million (£1.96m) bond in connection with the killing of District Attorney Mike McLelland, 63, and his wife Cynthia, 65, who were gunned down at their home in Kaufman County, east of Dallas, in March.

Investigators believe the double murder is linked to the killing of McLelland's main assistant, Mark Hasse, 57, who was shot dead in January.

It is not yet clear which murder or murders Williams has been charged with, and evidences against her have not been disclosed.

Williams's husband Eric Lyle Williams, 46, was arrested over the weekend and charged with making terrorist threats in connection to the case.

Investigators believe he sent an email to law enforcement officials threatening further attacks on local authorities if some demands the writer made were not met. The demands were not specified by authorities.

Furthermore, on the day of the arrest, investigators found more than 20 guns, including handguns and assault rifles, and a car similar to one spotted by eyewitnesses at the scene of Hasse's murder, in a storage facility rented by an associate of Williams upon the his request.

Last year, the former justice of the peace was convicted of stealing computer equipment from a county building in 2011. McLelland and Hasse led the prosecution.

The conviction brought Williams's carreer to an abrupt end. He has always maintained his innocence.

Early investigations into the Kaufman County's murders focused on a white supremacist prison gang - the Aryan Brotherhood of Texas - which criminal activities had also been the target of McLelland and Hasse.