Mark Hasse, 57, was shot execution-style outside the Kaufman County Courthouse Thursday morning after he got out of his car. Police are offering a $70,000 reward for the arrests of Hasse's killers, ABC News reported Saturday.
Witnesses said two masked gunmen dressed in black fled the scene in a silver sedan.
Police said they have no leads in the case, although said the Aryan Brotherhood of Texas, ABT, may be involved as Hasse's office was working on a racketeering case against the prison gang, ABC News reported.
The Dallas Morning News reported Thursday that "authorities with knowledge of the assistant DA's caseload (said) he had been heavily involved in the investigation of members of the Aryan Brotherhood."
On the same morning of the shooting, two ABT members pleaded guilty to racketeering charges in a Texas federal court, although Kaufman County Police Chief Chris Albaugh said that it "seems to be a coincidence" that the two events happened on the same morning.
"We're not ruling out any involvement until we know," Albaugh said. "And we have no specific information that the Aryan Brotherhood is a factor here."