From what I could make our from the articles available, Frederick Spears was arrested on the 18th of September for a domestic violence incident which happened on the 17th. Subsequently, he posted bond and was released on the same day he was arrested.
After his release, he inquired at the Ott Cribbs Public Safety Center (which houses the police station) about getting a ride back to Mary Spears' home to retrieve his vehicle. An officer drove him there and upon arriving, Frederick got into a verbal altercation with family members at the home. He was instructed by the officer to leave, and he complied.
ARLINGTON Homicide Investigation Report
There certainly may have been breaches of policy and procedure here by the Arlington PD, as either they knew about the PO and ignored it, or didn't check at all. Sure, it may just have been "human error" where those Frederick spoke to at the station had no knowledge of his crime and the PO against him, but it definitely raises questions about their policies and procedures.
As to why the PD offers rides, who knows... I'm wondering the same thing.
All JMO.