The family of a slain Philadelphia police officer has filed a federal lawsuit that contends the state parole board is to blame for his death.

The wrongful death and civil rights lawsuit filed Tuesday argues that Officer Moses Walker's alleged killer should have been behind bars.

Investigators said 23-year-old Rafael Jones was released from prison ten days before he and another man allegedly shot and killed Walker on Aug. 18 during a robbery as the officer walked home in street clothes after his shift.

The lawsuit said Jones was supposed to be under electronic monitoring and failed a probation office drug test but wasn't taken into custody as a judge had ordered.

Also named in the lawsuit are parole board chairman Michael Potteiger and Walker's parole officer, among others.