SEATTLE -- Prosecutors say an Auburn woman tried to hire a hit man to kill the father of her child and his family for $500, and even provided a piece of re-bar to be used in the murders.

What the woman did not know at the time was that the man she thought was a hired killer was actually an undercover sheriff's detective.

Elizabeth Beimer, 29, was charged Wednesday with solicitation to commit murder.

Investigators said Beimer's growing agitation over an ongoing custody battle with the father of her 6-year-old daughter was likely the motive.

According to court documents, Beimer repeatedly asked an acquaintance to have the man, his wife his parents killed.

The acquaintance told investigators that he tried to talk her out of it, but when he feared she would move forward with the plan on her own he contacted the intended victims and Auburn police.

Auburn police arranged for a King County sheriff's detective to contact Beimer, posing as a hit man.

The undercover deputy met Beimer at the White River Inn in Auburn, where she told the detective she wanted the father of her daughter and his wife killed, as well as the man's parents, if possible, the police report said.

In the report, investigators wrote that the whole conversation was captured on video, including Beimer agreeing to pay $500 for the killings.

Beimer and the undercover deputy discussed how the family should be killed, and in the end Beimer retrieved a piece of re-bar from her car that she said could be used to commit the murders, the report said.

"It was during that meeting Ms. Beimer brought pictures of the Davis family, floor plans and was very specific about how she wanted these members killed and the sequence she wanted them killed," said Sgt. Scott Near.

Beimer was arrested and allegedly confessed during a police interview to trying to have the four people killed.

Ruby Davis, one of the targets of the alleged plot, said she is in disbelief.

"You know, honestly, I don't see how anybody could want to do that," she said. "And what she was thinking, I don't know. I hope that she gets the help that she needs."

Davis' husband, Robert, is the father of one of Beimer's children and shares custody for a few hours every week. But according to the court document, Beimer wanted to ensure full custody by killing Robert, his wife and his parents.

"I don't hate her for what she was trying to do because she is the mother of my stepchild," said Ruby. "I just think of her that maybe it's just something in her head or maybe she just needs help."

Investigators believe Beimer wanted the murders to be carried out by Wednesday as she and Robert Davis were set to meet in family court on Thursday to reevaluate the child custody arrangements.

Beimer has four other children in addition to the one she had with Davis. The four children have been taken in to state protective custody.

If convicted, Beimer could face up to 20 years in prison. She is scheduled to be arraigned November 12.