Justin Smith, 23, is accused of killing 21-year-old Dianna Brice, according to Chesley Lightsey with the Philadelphia District Attorney's Homicide and Non-Fatal Shooting Unit.
Brice was found dead on April 5 in the 5800 block of Eastwick Avenue in Southwest Philadelphia. She had suffered multiple gunshot wounds to the head, police said.
Investigators believe Smith fatally shot Brice inside his car.
WATCH: Philadelphia DA's Office provides update on Dianna Brice murder case
That car was later found engulfed in flames in the area of 59th and Florence streets in Philadelphia just hours after Brice and Smith were seen at K Laundry in Yeadon on March 30.
No one was found inside the vehicle. The car was discovered about a mile from where police said Brice's body was discovered in the woods.
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On Sunday, Philadelphia police announced the arrest of 21-year-old Tylydia Garnett in connection with Brice's death. She is charged with arson, abuse of a corpse and related offenses.
Investigators say Garnett was seen on video buying gasoline before returning to a garage that was either rented or owned by Smith.
They loaded a heavy object into Garnett's car, which is believed to be Brice's body.
From there, investigators say Garnett followed Smith to the location on Eastwick Avenue where Brice's body was found.
Lightsey says Garnett fled to Florida after helping to dispose of Brice's body. She has been released after posting 10% of $75,000 bail.
The DA's office requested Garnett be held without bail but was unsuccessful.
"We asked that she be held without bail because she went above and beyond in her efforts to help this fugitive, both cover up his crime and flee from justice. We were given $75,000 of bail, 10% of that is $7,500. We appealed that that is still the number we have," said Lightsey.
Smith and Garnett are believed to be friends, but Lightsey couldn't speak further on how they knew each other.
Brice's mother, Betty Cellini, said her daughter had a young son and was 14 weeks pregnant. She also had a life-threatening medical condition that required medication.
Before Brice vanished, Cellini said the couple was involved in an argument.
"He goes, 'She don't want to even talk to me.' I said, 'I don't care, she's pregnant with your child,'" recalled Cellini.
Brice's family is hopeful that another arrest is coming soon.
"He is being hidden right now. There are people that are hiding him at this point. I wouldn't be surprised if he's going from house to house," said Kevin Ryan, a private investigator helping the victim's family.
Ryan said they believe someone's helping Smith evade law enforcement.
"The family's message is simple. Just come forward. No matter how small or how big the information is, it will definitely lead somewhere. Think of this as your daughter, your sister, your loved one," Ryan said.
Ryan said the family doesn't believe Brice knew Garnett.
"No, there's no connection that the family can think of," Ryan said.
Anyone with any information on Smith's whereabouts is asked to call police.