DALLAS — The mother of a black 15 year-old shot and killed by a white suburban Dallas police officer has asked to intervene in a civil rights lawsuit filed by the boy’s father.

Lawyers for Shaunkeyia Stephens filed the request to intervene in the lawsuit Tuesday. The lawsuit filed by Odell Edwards on behalf of the estate of Jordan Edwards alleges that the Balch Springs Police Department and city officials improperly trained the officer and should have noticed a pattern of escalating encounters with the public.

Lawyers for the Edwards family say Officer Roy Oliver, also named in the lawsuit, used a rifle to shoot at the vehicle as it was driving away, piercing a passenger window and striking Edwards. Oliver was fired and arrested last week on a murder charge.