Massachusetts man admits to killing his girlfriend as her children watched. Now his fate is up to a judge.

Thadius McGrath admitted Monday that he killed his girlfriend Samantha Rementer in the Northampton Township apartment they shared, strangling and beating her to death as her two young daughters sat nearby.

Now it will fall to a Bucks County judge to decide whether those actions were premeditated and amounted to first-degree murder.

McGrath, 37, pleaded guilty to murder in connection with Rementer’s death in June 2022, along with charges of endangering the welfare of children, reckless endangerment and related crimes. But he and his attorney, Keith Williams, say the killing was not premeditated, a requirement for a finding of first-degree murder, and asked the judge to sentence him instead to third-degree murder and spare him a life sentence.

Assistant District Attorney Thomas Gannon is hoping to prove that first-degree murder is the appropriate charge and set out to do that Monday at an evidentiary hearing that is expected to last two days.

Rementer, 31, met McGrath in 2021 through mutual friends of her late husband, according to her family. The two grew close, began a romantic relationship, and moved in together.

Police were called to the couple’s home in Northampton on June 8, 2022, by McGrath’s mother, who told them that he had called her sounding “rough and edgy,” according to audio of the 911 call played in court. He said he didn’t think he would be returning to Massachusetts as he had planned, telling her “This is goodbye. I love you.”

McGrath’s father, John, took the stand to say that he, too, received a phone call from his son, moments before the police knocked on his front door. In that call, he said, his son confessed to killing Rementer, and told his father he was going to jail. He then told his father to “have a nice life” as the call ended amid a gunshot.

When the officers arrived, the front door was locked, and their calls for McGrath went unanswered. Suddenly, Rementer’s then-5-year-old daughter came bursting out of the door, covered in blood, according to police bodycam footage presented at trial. The sight was so jarring that Northampton Township Officer John Kenney paused in the recording, visibly taken aback.

The girl later told police that her “mommy was dead,” beaten by McGrath with a lamp and stepladder because she was “getting on his nerves,” according to evidence presented in court. She also said she overheard McGrath shoot himself in the head, and that both the fatal beating and apparent suicide attempt were accidental.

In a recorded interview played in court, the girl said she saw McGrath hit her mother with the stepladder as she was lying prone and overheard her say “Please, Thad, I have two children.” McGrath said he didn’t care, according to the girl.

Investigators previously have said McGrath attacked Rementer after she had reminded him he was not the father of her children.

When Kenney, the Northampton officer, went into the home, he found Rementer’s then 2-year-old daughter still strapped into her high chair in the kitchen. The video played in court showed him pulling the toddler to safety, walking past blood stains on the walls of the apartment.

Later, in the children’s bedroom, Kenney and other officers found Rementer’s body covered in blankets, clothes and other items, as seen in the video. A stepladder was found nearby. The cord to a floor lamp had been wrapped tightly around Rementer’s neck, and she had a large gash across her chin.

Officers pronounced her dead at the scene.

In another bedroom, the officers found McGrath lying on the floor, covered in blood, with a 9mm pistol beside him. He was taken to St. Mary Medical Center, where doctors discovered he had suffered a self-inflicted gunshot wound to his face.

Nearly two years after surviving that injury, McGrath sat in silence Monday as the bodycam footage played in the Doylestown courtroom. He showed little emotion.

Meanwhile, on the other side of the room, Rementer’s family wept silently at hearing the 5-year-old recount the horrors she had seen.

The hearing is expected to conclude Tuesday.