Prosecutors say a tip from New Hampshire led investigators to a patched section of concrete and a murder charge against a 40-year-old man.
LOWELL, MA — Human remains found beneath the floor of a Tyngsborough garage are believed to be Jill Kloppenburg, a 47-year-old woman who disappeared from the Lowell area in January 2025, and prosecutors have charged Shawn Sullivan, 40, with murder in her death after a tip reopened the case.
The discovery brought a grim turn to a search that had stretched for more than a year and had left Kloppenburg’s friends hoping she would still be found alive. Prosecutors said the case moved quickly this month after Nashua, New Hampshire, police received a report that Sullivan had told someone he killed a woman named Jill and buried her under the garage floor of the home where he lived on Audrey Avenue in Tyngsborough. Investigators then linked that account to Kloppenburg’s missing-person case, searched the property and dug up human remains, leading to Sullivan’s arrest and arraignment in Lowell District Court.
Kloppenburg was last seen Jan. 2, 2025, leaving her residence on Broadway Street in Lowell, according to the FBI missing-person notice issued months after she vanished. Friends reported her missing on Feb. 26, 2025, and local investigators kept the case open as they tried to trace her last known movements and contacts. Prosecutors said Sullivan knew Kloppenburg and had been with her around the time she disappeared. The investigation took a major turn on March 10, 2026, when Nashua police got a call from a person who said a friend, later identified as Sullivan, had described killing a woman named Jill at his home and burying her in the garage. That information was passed along and checked against law enforcement databases, which showed an active Massachusetts missing-person case for Kloppenburg. By March 15, detectives from Tyngsborough, Tewksbury and the Massachusetts State Police had a search warrant and were at Sullivan’s home looking for evidence. What they found, prosecutors said, was a large section of the garage floor that appeared to have been patched.
Investigators used ground-penetrating radar to scan the garage and found what prosecutors described as an anomaly beneath the concrete. After breaking through the floor, they recovered a bag containing human remains. At first, officials said the remains had not yet been positively identified, but they quickly said they believed they belonged to Kloppenburg. In court the next day, prosecutors said dental records had identified the body as hers. They also said a preliminary autopsy found a through-and-through gunshot wound, with an entry wound to the chest and an exit wound to the back. Assistant District Attorney Ceara Mahoney told the court Sullivan eventually admitted Kloppenburg died in his home in February 2025. According to prosecutors, Sullivan said he was in bed with Kloppenburg, was falling asleep while holding a gun and twitched, causing the weapon to fire into her chest. Prosecutors said he told police she died soon after. Her body, Mahoney said, remained in his bedroom for a couple of days before he moved it to the garage, dug a hole into the concrete floor, placed her body there and sealed the opening with concrete and epoxy. Authorities have not publicly released a final autopsy report, and the full forensic timeline has not yet been laid out in court.
The case has drawn attention not only because of the condition in which the remains were found, but also because of the long gap between Kloppenburg’s disappearance and the discovery under the garage. Kloppenburg had been living in temporary housing with roommates when she was last seen. Prosecutors said her phone was last used on Jan. 14, 2025, a detail that suggested to investigators that some activity continued after the date she was last physically seen. Friends said for months that it was unlike her to stop answering calls and messages, and they repeatedly searched for her. They also said the Tyngsborough home later searched by police had been a place she considered safe. The FBI eventually circulated a public notice that included her age, height and identifying tattoos, adding national visibility to a local case that had gone unsolved. When authorities announced the garage-floor discovery, Tewksbury Police Chief Ryan Columbus said it was not the outcome anyone had hoped for, but that it could finally bring answers to Kloppenburg’s family and friends. Tyngsborough Police Chief Shaun Woods said the disappearance had remained under active investigation for more than a year, underscoring that the case had never been closed even as public information remained limited.
Sullivan was charged with murder, assault and battery with a dangerous weapon causing serious bodily injury, and improper disposal of human remains. A plea of not guilty was entered on his behalf at his Tuesday arraignment in Lowell District Court, where a judge ordered him held without bail. His lawyer argued that the evidence pointed to a fatal accident rather than a malicious killing, calling it a tragic mistake followed by panic. Prosecutors took a sharply different view, pointing to the alleged burial beneath the garage floor, the yearlong silence and Sullivan’s initial false statements to investigators before what they described as a later admission. The court record so far leaves several questions unresolved, including what happened between Jan. 2, 2025, when Kloppenburg was last seen leaving her Lowell address, and the time prosecutors say she was shot in February 2025 inside Sullivan’s home. Authorities also have not publicly detailed whether anyone else in the house knew a body had been buried in the garage or whether more charges could follow. Sullivan is due back in court on April 17 for a probable cause hearing, and investigators have said the case remains active as forensic testing and witness interviews continue.
The search scene stunned neighbors on Audrey Avenue, where residents watched officers work from early morning into the evening before jackhammers and a police tent appeared at the garage. Neighbor Joseph McRell said the activity grew more alarming as the day went on and it became clear investigators were breaking into the floor. Another neighbor, Ella White, said police were everywhere and the scene felt chaotic. Outside the courthouse, Kloppenburg’s friends spoke through tears and anger after hearing prosecutors describe the burial. One friend said Kloppenburg was a mother, a sister, a daughter and a friend, while another rejected the defense claim that the shooting was only a mistake, pointing instead to the steps prosecutors say Sullivan took afterward. A childhood friend of Sullivan said the allegations were hard to process but added that the person who reported the confession did the right thing by coming forward. Those reactions captured the split emotions now surrounding the case: grief from people who had searched for Kloppenburg for months, shock from neighbors who lived beside the garage where the remains were found, and new scrutiny on how a disappearance from early 2025 ended in a murder prosecution more than a year later.
As of Tuesday evening, prosecutors had identified the remains as Kloppenburg’s and Sullivan was being held without bail. The next public step in the case is his April 17 probable cause hearing, while investigators continue to sort out the final forensic record and the full timeline of what happened inside the Tyngsborough home.
Author note: Last updated March 17, 2026.