By CBS3 Staff

PHILADELPHIA (CBS) – Philadelphia police have released the mugshot of 17-year-old Xavier Johnson after he was charged in the murders of his foster mother and a 20-year-old missing man. Police say Johnson stabbed to death 64-year-old Renee Gilyard, of East Germantown, and Jimmy Mao, of West Philadelphia, in separate incidents.

Philadelphia Police Capt. Jason Smith said Xavier “brutally tortured and murdered” both of his victims.

He said robbery appeared to be the motive for both incidents.

From left to right: 20-year-old Jimmy Mao and 64-year-old Renee Gilyard

Gilyard was Xavier’s foster mother for only three days before she was killed. She was found stabbed to death early Wednesday morning inside her East Germantown home. Her body was found covered in blood in a bathtub.

Police say Johnson was taken into custody Wednesday morning in West Philadelphia after stealing and crashing Gilyard’s SUV following a police chase.

Police also confirmed Mao’s remains were found inside a black duffel bag on the 1000 block of Cobbs Creek Parkway, late Wednesday afternoon. Mao went missing in late December.

Mao suffered stab wounds to his face and neck. Smith says Johnson placed Mao’s remains inside a duffel bag and threw it down a hill in an attempt to conceal his death.

Johnson has been charged with murder, robbery, possessing instruments of crime, tampering with evidence, obstruction of justice, abuse corpse and theft-receiving stolen property.