Frank Rzucek is the father of Shanann and grandfather to her two children, all of whom were killed by son-in-law Chris Watts in August 2018.
"For the past 11 months, piled on top of pain and the grieving of this devastating loss, our family has been subject to horrible, cruel abuse, outright bullying, on a daily basis," Rzucek told reporters outside Watts' former Colorado home.
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Rzucek said the attacks on his family include threats, fake Facebook accounts and a constant stream of insults.
"It is cruel, it is heartless," Rzucek said.
He pointed out that re-victimization of families who have lived through tragedies is nothing new. He said families of those killed at Sandy Hook Elementary School in Connecticut in 2012 have for years been targeted by harassers and conspiracy theorists.
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"Families like ours should have the right to be safe...the right to mourn in peace," Rzucek said. "To Congress, or to any person in position of power, we are calling on you to do something to pass laws that will protect victims of unspeakable crimes from this kind of abuse."
In November 2018, Watts pleaded guilty to the murder charges against him. In exchange for doing so, he avoided the death penalty.
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Watts told investigators he strangled his wife at their home. He then put her body in a car and drove with his two daughters -- 4-year-old Bella and 3-year-old Celeste -- to the site of his former employer, Anadarko Petroleum -- one of the state's largest oil and gas drillers.
There, Watts strangled both of his children with Celeste's blanket.
He left their bodies inside oil and gas tanks that "were mostly full."
Investigators believe Watts placed them in there to conceal the smell from passersby.
After confessing to the murders, Watts told investigators that he was not "coherent enough" to know that he was going to kill his daughters.
"No father would ever want to do anything to hurt his blood and flesh, but I did that and I just don't understand how it happened."
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