Authorities believe the 20-year-old New Jersey man accused of killing a college student and another woman in the last few months may be linked to a third slaying, and investigators are actively looking at him as a possible serial killer, law enforcement sources familiar with the probe tell NBC 4 New York.

The sources say Khalil Wheeler-Weaver is being investigated in the death of a missing 19-year-old Philadelphia escort whose burned body was discovered in an abandoned building in Orange, New Jersey. Though she has not been publicly identified, she was living at the Garden State Motel in Union Township when she disappeared, the sources say. She vanished in September.

It wasn't clear what investigators believed tied Wheeler-Weaver to the case, but the body of at least one of the other women he's accused of killing was found under similar circumstances.

He has not been charged with killing the 19-year-old woman. His attorney, Shevelle McPherson, didn't immediately respond to a request for comment on a possible connection to the case.

On Tuesday, Wheeler-Weaver pleaded not guilty to murder charges in the death of 33-year-old Joanne Brown, who was last seen Oct. 22 in Orange and whose body was found in a vacant house in Newark on Dec. 5.

He has also pleaded not guilty to murder and other crimes in the death of 20-year-old Sarah Butler, a sophomore at New Jersey City University who was reported missing Nov. 23. The Montclair woman's body was found eight days later on the Eagle Rock Reservation.
  
Investigators said Butler and Brown didn't appear to know each other, but both were killed in the same manner: strangulation and asphyxiation. Police have not revealed potential motives in the slayings. 

Wheeler-Weaver remains jailed on $5 million bail. 

Butler's sister told NBC 4 New York Tuesday, before news broke of the possible connection to the third slaying, that she wasn't surprised Wheeler-Weaver had been accused of more deadly violence — but she did say she was stunned.

"Usually I just hear about this in movies," Aliyah Butler said. "I didn't think that things like this and people actually happened in the real world." 

"Now I'm wondering how many girls he's hurt like this," she said. "I'm just hoping the number isn't large because what he did to my sister was terrible."

Asked whether they believe the deaths are the work of a serial killer, acting Essex County Prosecutor Carolyn Murray said Tuesday, "I'm not gonna comment on that."

McPherson insists her client is innocent and that prosecutors don't have enough evidence to connect him to the deaths of Brown and Butler.

She said Tuesday the evidence she has seen is "very circumstantial."

"They're trying to accuse him of this [second] crime, because manner of deaths are similar," she said. "If they're gonna try to secure a conviction based on manner of death, they're gonna have to come up with more than that."

NBC 4 New York has learned Wheeler-Weaver comes from a family that includes at least two law enforcement officers -- one a cop in East Orange who lives in his home and another who works for the Newark Police Department. 

Wheeler-Weaver was most recently employed as a security guard for Sterling Security, a firm owned by two former Newark police officers. In that capacity, he worked at a Shoprite in Union Township.

The security firm didn't immediately respond to a request for comment.