DALLAS—A Texas prison inmate who threatened prosecutors as they targeted alleged white supremacist gang members must serve nearly five years in a federal lockup.

A judge in Dallas on Friday sentenced 28-year-old Jesse Brister of Conroe. The gang member in September pleaded guilty to mailing threatening communications.

Authorities say the hoax letters drew resources away from investigations such as the killing of Kaufman County District Attorney Mike McLelland and his wife, plus the slaying of assistant DA Mark Hasse (HA'-see).

Authorities say Brister last March mailed letters to the U.S. attorney's office in Dallas threatening retaliation for prosecution of Aryan Brotherhood members. A task force included Kaufman County law enforcement.

Brister at the time was in a state prison for fraud. He must now serve 55 months in federal prison.