Murder charges were filed against Keon King on Wednesday after the Philadelphia medical examiner ruled the cause of Kada Scott’s death a homicide, according to the city’s district attorney’s office.

New charges filed against King, 21, include murder, robbery, theft, tampering with evidence, abuse of corpse, obstruction of justice and related offenses. He was previously charged with kidnapping and arson, among other crimes.

Scott’s body was found in a shallow grave on Saturday at Ada H. H. Lewis Middle School in East Germantown.

In court records made public Wednesday morning for arson and conspiracy charges filed against King, investigators detail cellphone evidence that they say connects King’s cellphone to areas linked to Scott’s disappearance and where her body was found. The document also includes information on text messages exchanged between King and Scott right before she disappeared.

The records, obtained by CBS News Philadelphia, show Scott received a dozen calls on the night of Oct. 4 from a phone that traces back to King. The calls began at 9:25 p.m. and continued until 10:12 p.m., according to court documents. This is the same period police say Scott was arriving for work at a Chestnut Hill assisted living facility.

Scott, according to court papers, texts, “kidnap me again.” King replied, “better be up too,” followed by plans to meet later that night.

At the same time, a coworker sees an upset Scott with court records alleging she’s overheard on the phone saying, “I can’t believe you’re calling me about this [expletive],” court documents show.

The last exchange happens at 10:09 p.m. with the words “cm when u here,” or call me when you’re here, according to court documents.

Scott is seen leaving work in a dark colored car described as the suspect vehicle, a 2008 Hyundai Accent. Sources previously told CBS News Philadelphia their investigation found that Scott was killed 20 minutes after she left work.

In court records, investigators say cellphone data shows Scott and King arrived together in Awbury Rec Center’s parking lot next to Ada H. H. Lewis Middle School. Surveillance cameras picked up their arrival and showed the car backing into a parking spot.

At 10:24 p.m., Scott’s cellphone stops transmitting a signal, court documents show. Scott was reported missing on Oct. 5.

Twenty-four hours later, the night of Oct. 5, police say a Toyota Camry owned by King pulls into the rec center parking lot. Two people exited the car and are seen going to the vacant middle school.

Hours later, court records allege they return to the car, remove a heavy object consistent with a human body and move in a direction beyond the parking lot into the area where investigators say Scott’s heavily decomposed remains were found in a shallow grave last Saturday.

Police say the Hyundai Accent was set on fire on Oct. 7.

On Oct. 9, police executed a search warrant at a home in the 5500 block of Belmar Terrace and found three phones, one tablet, contractor bags, latex gloves, a hammer and 9mm ammunition, according to court documents.

Prosecutors say they were able to piece together King’s alleged involvement by tracking his cellphone as well as picking up his movements on surveillance cameras.

The day after the car was torched, police made an urgent plea to the public for help in finding Scott.

King declined a police interview after he turned himself in on Oct. 14, court documents show.

“Our office remains in continued communication with the parents and family of Kada Scott, keeping them informed of new developments in the investigation and prosecution of this case,” the DA’s office said in a statement announcing murder charges.  

King is being held on $500,000 cash bail and will be due back in court for arraignment on the murder charge.

CBS News Philadelphia reached out to King’s attorney, Shaka Johnson, and has yet to hear back. Â