Prosecutors provided more information about the murder of an 18-year-old pregnant woman at an arraignment for her on-again, off-again boyfriend who is now charged with her death.

Investigators say that Gregory Groom, 22, admitted killing Kylee Monteiro and burying her body on his property in Rehoboth, Massachusetts, ABC News reported.

Monteiro, who was 12 weeks pregnant and living in a shelter for pregnant and homeless women, was last seen on August 6 when she went to Groom’s home, as CrimeOnline reported. Family and friends said she indicated she didn’t feel safe and then stopped responding.

Groom contacted police on August 8 and told them Monteiro had been “at his house, she was looking for a place to stay, they got into an argument and that she ultimately left the residence,” prosecutors said in court on Wednesday.  He further said Monteiro “hadn’t been seen or heard from since,” they told the court.

Groom said the argument they had was over whether he would allow her to stay at his property.

On the night before her disappearance, prosecutors said, she texted her sister, Faith Monteiro, and told her that Groom “threw me on the ground and pulled my hair and strangled me,” WJAR reported. At one point, they said, Monteiro texted her sister that her “phone is at 4% and if I die, it was Greg.”

When family tried to reach her to get her to a safe location, she told them that she was “attempting to continue to stay at Mr. Groom’s residence,” ABC News said.

Officials searched Groom’s 25-acre property on August 14 but found “nothing of significance.”

On Tuesday of this week, things changed dramatically when Groom reported to police for another interview. At that point, he told them that they’d argued and that he “pushed her, she fell backwards and she hit her head.”

Monteiro tried to contact someone, but Groom said he told her he would “knock her cellphone out of her hand,” prosecutors said.

Detectives further pressed Groom on Monteiro’s whereabouts, telling him the were “prepared to search the property and dig if necessary.”

At that point, prosecutors said, Groom drew a “rudimentary map” showing a shed on his property, telling them the argument took place behind that shed, WJAR reported. And he confessed that he had stabbed the teen “twice in the neck and once in the chest,” adding that the chest thrust broke the knife’s blade.

Then, he said, he spent “several hours” digging a hole in a woods about 20 yards from the shed, where he “pushed her body into a hole and covered it up,” ABC said.

Officers went to the property, where the found a “large pile of brush” and a “body consistent with Kylee Monteiro.”

The body is currently with the medical examiner for positive identification and an autopsy.

Groom has been charged with murder, assault and battery on a pregnant victim, assault and battery on a family or household member, and aggravated intimidation of a witness, juror, police, or court official.

Bristol Count District Attorney Thomas M. Quinn said after the hearing that it was “still too early” to determine a motive for the murder.

Groom is being held without bond and is due back in court next month for a probable cause hearing.