(CNN) A woman is in custody and a toddler is missing after the child's father said a driver abducted his daughter on Saturday evening in Penn Hills, Pennsylvania, according to police documents and a news release.

Paul Johnson said he was riding in a car with Lyft and Uber stickers with his daughter and two friends, according to a criminal complaint filed by the Allegheny County police.

The driver of the car was Sharena Nancy, a woman with whom Johnson was in the beginning of an "intermittent romantic relationship" with, Allegheny County Police Superintendent Coleman McDonough said at a press conference Tuesday.

The couple became acquainted over social media in the past few months and spent several hours together with Johnson's daughter and another friend on Saturday, before an argument ensued while the woman was driving, McDonough said.

While police did not elaborate on the details of the argument, McDonough said it was significant enough that Johnson and his other friend decided to exit the car.

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