Mario Echeverria, 18, pleads guilty to hindering prosecution in fatal hit-and-run of Anna Dieter-Eckert, 6, and Abigail Robinson, 11, in Portland, Oregon

A Forest Grove teen pleaded guilty Thursday in connection with the crash that killed two young stepsisters playing in a pile of leaves in October. Mario Echeverria, 18, was sentenced to 13 months in prison for hindering prosecution after the crash, according to the Washington County District Attorney's office. Police said he and 18-year-old Cinthya Garcia Cisneros were driving home Oct. 20 when they hit and killed 11-year-old Abigail Robinson and 6-year-old Anna Dieter-Eckert, who were playing in the leaves near their home. Court documents showed Cisneros was driving the SUV. Police said she felt a big bump after driving through the leaf pile but didn't stop. Her younger brother returned to the scene and found Cisneros had run over a child. Instead of going to police, investigators said Echeverria took the SUV to a car wash to destroy evidence. According to Oregon sentencing guidelines, someone with no criminal record would likely get probation for hindering prosecution. But as a juvenile, Echeverria was convicted of 1st degree sodomy, so the sentencing guidelines were stricter for him. Cisneros remains in custody. She had pleaded not guilty to failure to perform the duties of a driver to injured persons.