POMONA (CBS) — A Rowland Heights woman convicted of smothering her two young sons with a pillow and killing her husband with a sword as he slept was sentenced to death Thursday.

Manling Tsang Williams, 32, was convicted in 2010 in the August 2007 killings of her 27-year-old husband, Neal, and sons, Ian, 3, and Devon, 7.

Williams was found guilty of three counts of first-degree murder and found true the special circumstance allegation of multiple murders and lying in wait. But that jury deadlocked on what sentence to recommend, with eight of the 12 jurors favoring a death sentence.

Deputy District Attorney Stacy Okun-Wiese told the jury during the closing arguments in the penalty phase of Williams’ trial that she waited for her family to go to sleep and then “went in for the kill.”

The young mother, 29 at the time, put on a pair of gloves, took a pillow and held it over her 3-year-old son’s face until he lost consciousness, the prosecutor said. She then climbed the bunk bed stairs to her oldest son’s bed and put the pillow over his face as she took “every last breath of air he has,” Okun-Wiese told jurors.

The prosecutor said Williams returned to her computer, checked out the Myspace page of the lover who had suggested she get a divorce, then went out with friends. When she returned home, she chose the heaviest, sharpest sword in the house to attack her sleeping husband on Aug. 8, 2007.

“The defendant killed her own family for no reason other than her selfishness,” Okun-Wiese told jurors, adding that Williams “wanted to be free” to be with the man with whom she was infatuated in high school.

Defense attorney Thomas Althaus said his client would forever suffer from the consequences of what she did and that she would be “severely punished” for the murders.”

“I’m not saying she didn’t commit the crimes,” Williams’ attorney said. But he disputed the prosecution’s contention that the killings were premeditated, noting his client’s statement that everything happened after a fight.

Althaus said his client, who previously had been described as a kind and caring woman, experienced learning disabilities, difficulties in school, physical abuse and repeated criticism while trying to please her mother.

He noted that she had no prior history of violent criminal activity and urged jurors not to let anger or emotion dictate their decision.

(©2012 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. Wire services contributed to this report.)