PHILADELPHIA (CBS) — A 17-year-old boy was charged Thursday with the murders of his 64-year-old foster mother and a 20-year-old missing man. Philadelphia police say Xavier Johnson stabbed to death both 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.

“Robbery appears to be the motive for both incidents,” Smith said.

Police just announced charges against the 17 y/o in the murders of Jimmy Mao and Renee Gilyard, saying robbery appears to be the motive in both cases https://t.co/2MNe73e0Cf — Matt Petrillo (@MattPetrillo) January 16, 2020

Police say when Xavier entered Gilyard’s home earlier this week, he was set on stealing money and taking her SUV. Police also revealed the suspect stole a PlayStation and money from Mao.

Gilyard was found stabbed to death early Wednesday morning inside her East Germantown home. Her body was found covered in blood in a bathtub.

Xavier was taken into custody Wednesday morning in West Philadelphia after crashing Gilyard’s SUV following a police chase.

Gilyard was Xavier’s foster mother for only three days before she was killed.

Acting Philadelphia Police Commissioner Christine Coulter said Gilyard was the mother of a Philadelphia police officer.

“To live through any death is a horrible experience, but to know you’re mother is murdered is a terrible thing,” Coulter said.

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

“We found a knife. We’re going to do an examination on the knife we recovered to determine whether it was the murder weapon, but there’s a good possibility that it is,” Smith said.

Smith added it’s possible it’s the same knife that was used in the stabbing death of Gilyard.

“It’s possible it’s the same knife because we know there were two knife wounds to Ms. Gilyard, when she was discovered. It’s also possible that it was a knife taken from her home,” Smith said.

Mao went missing in late December.

According to family members, Mao had just moved into a foster home on Angora Terrace with the suspect. Days after, police say Xavier stabbed Mao to death before disposing of his body less than a block away from the foster home.

Investigators are being tight-lipped over exactly how they connected Xavier to Mao’s murder.

“We developed information in our investigation,” Smith said. “I can’t be more specific than that. It would divulge too much.”

Smith added that missing 16-year-old Jacob Merritt-Richburg may have information in Mao’s homicide, but is not considered a suspect.

The city’s Department of Human Services says they are “heartbroken over the recent deaths” and are supporting the police in their investigation.

“We are saddened by the lives cut short — a foster parent whose commitment to community meant fostering children who needed a safe home, and a young person who had his whole life ahead of him,” the department said in a statement.

Xavier had five prior arrests for aggravated assaults.

CBS3’s Matt Petrillo contributed to this report.