Williams, 37, was executed at the state prison in Huntsville about an hour after the U.S. Supreme Court rejected his final appeal, KWTX-TV, Waco, reported.
Authorities said Blando was driving through a Houston hotel parking lot when he saw Williams behind the wheel of a stolen Lexus. Williams got out of the car and when Blando approached him with his gun drawn, the two struggled. Williams pulled out a gun and shot Blando in the chest while the officer was trying to handcuff him, authorities said.
Williams fled but was apprehended a short time later with the handcuffs still dangling from his wrist.
Williams told police he thought Blando, who was in plainclothes and in an unmarked vehicle, was trying to rob him and contended he fired in self-defense.
Another officer testified, however, that Blando was wearing his badge around his neck.
Williams' attorneys argued unsuccessfully for a delay in his execution, requesting the courts be given time to review their claims he had deficient legal help at trial and in the early stage of his appeals.
The TV station said a state district judge in another case Wednesday granted a 60-day stay of the execution of inmate Robert Pruett, who was scheduled to die next Tuesday for stabbing a Texas prison guard to death.