FOREST GROVE, Ore. The alleged driver arrested Tuesday evening for hitting and killing two young Forest Grove stepsisters intentionally ran over a leaf pile and later found out she had hit someone but never came forward, documents show.

Cinthya Garcia Cisneros, 18, of Forest Grove was arrested Tuesday with her boyfriend, 18-year-old Mario Echeverria of Cornelius for hitting and killing Abigail Robinson, 11, and her 6-year-old stepsister, Anna Dieter-Eckerdt, who were playing in the leaves near their home Sunday evening.

Background: Two teens arrested in connection with Forest Grove girls' deaths

Attorneys for Cisneros and Echeverria entered not-guilty pleas in a Washington County Court Wednesday.

Police said a tip from a citizen who saw news coverage of the girls' deaths led them to question the pair.

According to the court documents released to KGW Wednesday, Echeverria and Cisneros first denied having knowledge of the crash when police questioned them.

Several minutes later, Echeverria told police Cisneros was driving and he heard a bump after she intentionally ran over a large pile of leaves on Main Street in Forest Grove. Echeverria admitted he was a passenger in the vehicle.

When detectives further interviewed Cisneros, she admitted she was driving. She also said the bump was enough to cause her concern and that it damaged the vehicle, according to the court documents.

The third person in the vehicle, Cisneros brother, went back to the scene of the crash and learned children had been hit, then returned to tell her she had run over a child, the court documents said.

Instead of returning to the scene, court documents show Echeverria took the SUV to a car wash to get rid of evidence.

Cisneros told police she was scared to come forward and the vehicle belonged to Echeverria s mother, documents show. Cisneros reportedly lives only a couple of blocks from the scene of the crash and made no effort to contact the victims' family or law enforcement on Monday or Tuesday.

She was charged with two counts of failure to perform the duties of a driver to injured persons. A grand jury will review the evidence and decide if the charges will be changed to include hit-and-run.

Echeverria faces charges of tampering with evidence and hindering prosecution.

More: Police find SUV, arrest 2 teens in girls' deaths

Police said Abigail's father, Tom Robinson, had been taking photos of the girls as they played in the leaves. He went in the house briefly, heard a car go by and came out to find the girls had been hit and were injured. His wife Susan Deiter is Anna's mother and he is her stepfather.

Anna died at the scene. Abigail died at Randall Children s Hospital Monday night.

More: Fundraisers for families of Forest Grove girls


KGWreporter Mark Hanrahan contributed to this report.

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