Updated

11:15 am.

A prosecutor says a 15-year-old Pennsylvania girl who survived a knife attack that left her mother and sister dead ran upstairs and identified the killer to neighbors.

The girl says Leeton Jahwanza Thomas' wife was friends with her mother. Police arrested him minutes later. They say a K-9 unit traced his scent from an open window at the crime scene to his home.

The 37-year-old Thomas was charged in April with molesting the girl's 16-year-old and 13-year-old sisters. The 16-year-old died in the stabbings; the 13-year-old wasn't home.

Lancaster County District Attorney Craig Stedman tells The Associated Press on Friday the motive appears to be retaliation to silence the family. He says there's evidence the victims tried to escape.

The 15-year-old is in stable condition. Investigators haven't been able to talk to her.

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8:55 a.m.:

Prosecutors say a suspect in a child sex assault case fatally stabbed a Pennsylvania woman and her 16-year-old daughter, who were witnesses against him.

The woman's 15-year-old daughter was severely wounded in the attack early Thursday in rural Lancaster County, about 70 miles west of Philadelphia.

Leeton Jahwanza Thomas is charged with two counts of criminal homicide, one count each of attempted homicide and burglary.

He is jailed without bail pending a June 22 preliminary hearing. Online court records did not list a lawyer to comment on the charges.

The 15-year-old is listed in critical but stable condition.

Court records show the 37-year-old Thomas posted $5,000 bail on April 18 while facing charges of aggravated indecent assault involving children.

District Attorney Craig Stedman calls the killings a "nightmare situation."