By Lisa Maria Garza

DALLAS (Reuters) - A Texas jury that convicted a former Texas justice of the peace of murdering a prosecutor's wife in a revenge plot, heard arguments on Monday in the penalty phase of the trial, in which it could sentence him to death.

Eric Williams, 47, was found guilty last week in the killing of Cynthia McLelland in 2013. He has also been charged with murdering District Attorney Mike McLelland and Kaufman County Assistant District Attorney Mark Hasse to get back at them for obtaining a theft conviction that cost Williams his job and law license, prosecutors said.

Prosecutors, who are seeking the death penalty, have indicated they could bring Williams to trial for the other two deaths, depending on what happens in the current case. Jurors in the Dallas suburb of Rockwall will hear more testimony on Tuesday.

Lawyers for Williams did not make opening statements and have not yet called any witnesses.

Hasse was gunned down outside the Kaufman County Courthouse on Jan. 31, 2013, and the McLellands were shot to death inside their home on March 30, 2013.

Williams, dressed as a "masked assassin," walked toward Hasse and opened fire, continuing to shoot him after he collapsed to the ground, prosecutor Bill Wirskye told jurors.

Prosecutors presented a dashcam video from the patrol car of a police officer that showed the Hasse killing, and jurors heard from witnesses who saw the shooting and attempted to save Hasse's life after the gunman fled.

Witness Patricia Luna said when she came outside, Hasse was on the ground and a woman was giving him CPR.

"I’ve never seen that much blood in my life," Luna said

Williams' wife, Kim, is also charged with capital murder and will be tried separately. No date has been set for her trial.

(Reporting by Lisa Maria Garza; Editing by Jon Herskovitz, Eric Beech and Peter Cooney)