When Sarah Butler did not return to her home in Montclair, N.J., after borrowing her mother’s minivan in November 2016, her family immediately recognized that she might be in trouble.
Using Ms. Butler’s computer passwords to log on to her email and social media accounts, one of her sisters and two friends found one of the last men she had been talking to online. Then they set up a meeting with him at a Panera Bread cafe in Montclair, with the police waiting in the parking lot.
At the time, the police considered the man, Khalil Wheeler-Weaver, then a 20-year-old security guard from Orange, N.J., only a person of interest in Ms. Butler’s disappearance.
But the trap that Ms. Butler’s sister and friends laid on Nov. 26, 2016, helped detectives identify Mr. Wheeler-Weaver as a suspect and, eventually, a serial killer, the authorities said.
On Wednesday, nearly five years later, Mr. Wheeler-Weaver, 25, was sentenced to 160 years in prison for murdering Ms. Butler, 20; Robin West, 19, of Union Township; and Joanne Brown, 33, of Newark; and for kidnapping, sexually assaulting and attempting to murder Tiffany Taylor. All four were attacked from August to November in 2016.
Adam B. Wells of the Essex County Prosecutor’s Office, the lead prosecutor in the case, credited Ms. Butler’s sister and friends with orchestrating the first in-person meeting between the Montclair police and Mr. Wheeler-Weaver, giving detectives “a big early break” in the investigation.
“They really did go above and beyond what people often do,” he said in an interview. “It’s a testament to their love of their friend and sister.”
Ms. Butler was a student at New Jersey City University when she began talking to Mr. Wheeler-Weaver on Tagged, a social networking site, where he went by the name LilYachtRock.
After she borrowed her mother’s minivan to meet him on Nov. 22, 2016, Mr. Wheeler-Weaver strangled her, the authorities said. Her body was found in Eagle Rock Reservation in West Orange on Dec. 1, 2016.
Before her body was found, the police had opened a missing-person investigation. At the same time, Ms. Butler’s sister Bassania Daley and two friends, LaMia Brown and Samantha Rivera, began their own detective work.
Because Ms. Brown knew Ms. Butler’s computer passwords, they were able to log on to her social media accounts and discovered that Ms. Butler had been talking to LilYachtRock on Tagged, Mr. Wells said.
Ms. Rivera created her own profile on Tagged. Within an hour, LilYachtRock had contacted her and started pressing her to meet him in person, Mr. Wells said.
Ms. Rivera was at the police station in Montclair, hoping to tell detectives that she had just been contacted by the last man who had communicated with Ms. Butler, when he called her on her phone, Mr. Wells said. Ms. Daley pulled out her phone and recorded the conversation.
Ms. Rivera arranged to meet him at Panera and waved to him when he pulled up in a BMW, Mr. Wells said.
That was when the police, who were waiting in the parking lot, stopped Mr. Wheeler-Weaver and questioned him about Ms. Butler’s disappearance.
Mr. Wheeler-Weaver wasn’t immediately arrested because Ms. Butler’s body had not yet been found, and he was considered only a person of interest, not a suspect, Mr. Wells said.
But the way he had reached out so quickly to Ms. Rivera heightened detectives’ concerns about him, and he gave an alibi that later unraveled, Mr. Wells said.
“Getting this initial contact with Wheeler-Weaver was a big early break,” Mr. Wells said. “It gave us more reason to be suspicious of him.”
Mr. Wheeler-Weaver was arrested days later, after Ms. Butler’s body was found. Ms. Daley, Ms. Brown and Ms. Rivera did not respond to messages left at numbers listed under their names. Their role in cracking the case was previously reported by NorthJersey.com.
Although he could be outwardly charming, Mr. Wheeler-Weaver tortured and strangled women who were poor, homeless, mentally ill or engaged in sex work, the authorities said.
The police found that he had searched online for anesthesia and drugs to “put someone to sleep,” as well as for homemade poisons, the authorities said.
Investigators also found a body-fluid cleanup kit, zip ties and lighter fluid in the trunk of the car where he had assaulted Ms. Taylor in November 2016, the authorities said.
After Mr. Wheeler-Weaver murdered Ms. West on Sept. 1, 2016, he set fire to her body and torched an abandoned house where he had left her, the authorities said.
Her remains were so badly charred that she had to be identified with dental records.
“He thought all of the victims would not be noticed,” Judge Mark S. Ali said while sentencing Mr. Wheeler-Weaver in Superior Court in Essex County on Wednesday. “He thought all of the victims eventually would be forgotten.”
Mr. Wheeler-Weaver, reading from a sheet of paper, maintained his innocence.
“I have clear and convincing evidence that I was set up, I was lied on and I was framed by the Essex County Prosecutor’s Office,” he said.
During the hearing, Ms. Taylor rejected Mr. Wheeler-Weaver’s claims. Ms. Taylor, who was kidnapped and assaulted by Mr. Wheeler-Weaver seven days before Ms. Butler was killed, pointed out that she had previously met Mr. Wheeler-Weaver at his home and recognized him when he assaulted her.
During the attack, Mr. Wheeler-Weaver had handcuffed her, put duct tape around her head and had started to cover her nose and mouth, Judge Ali said. But Ms. Taylor was able to slip one hand from the handcuffs and then escape when she locked her hotel room door, leaving Mr. Wheeler-Weaver outside.
Ms. Taylor said that since the attack, she does not do her hair or use makeup and does not have or want friends.
“I don’t trust anyone,” she said. “I’m always paranoid. But I’m just happy to still be here and be able to tell what happened so that he could be locked up for it.”