Investigators say a report to New Hampshire police set off a search in Tyngsborough that ended with the recovery of human remains believed to be a missing Lowell woman.
TYNGSBOROUGH, Mass. — A phone call to police in New Hampshire set off a homicide investigation in Massachusetts that ended with human remains being dug from beneath a garage floor, where prosecutors say a missing woman may have been buried for more than a year.
Middlesex County authorities said Monday that they believe the remains found at a Tyngsborough home are those of Jill Kloppenburg, 47, who vanished in early 2025. Shawn Sullivan, 40, of Tyngsborough, is expected to face charges including murder, assault and battery with a dangerous weapon causing serious bodily injury, and improper disposal of human remains. The remains have not yet been formally identified, but prosecutors said the evidence uncovered at the house strongly points to Kloppenburg, whose disappearance had troubled relatives and investigators for months.
District Attorney Marian Ryan said the investigation broke open on March 10 after Nashua police received a report from someone who said a friend had confessed to killing a woman named Jill. Authorities identified that friend as Sullivan. Ryan said the witness told police Sullivan claimed he had shot the woman and buried her beneath the floor of a garage. Detectives from Tyngsborough, Tewksbury and the Massachusetts State Police followed up on the information and obtained a search warrant for Sullivan’s home on Audrey Avenue. When they entered the garage Sunday, investigators spotted a large repaired section of concrete. The area, roughly 5 feet long and 3 feet wide, drew immediate attention because it appeared newer than the surrounding floor.
Investigators then used ground-penetrating radar to scan the garage and found something below the surface, Ryan said. After cutting through the concrete, they recovered a plastic bag containing human remains. That grim discovery transformed the search from a missing-person inquiry into a murder prosecution. Officials cautioned that the Office of the Chief Medical Examiner still must confirm the identity of the remains with forensic testing and determine a cause of death. Prosecutors nonetheless said they believe the victim is Kloppenburg. Ryan said Kloppenburg and Sullivan knew each other, that she had been inside his home before, and that investigators believe he had been with her near the time she disappeared. Authorities have not said whether anyone else may have been present when she was last seen.
The public timeline remains incomplete, but prosecutors have outlined key points. Kloppenburg was reported missing in February 2025 by friends in Tewksbury. Ryan said those friends told police they had not been in contact with her since November 2024, while other reporting on the case has placed her last known cellphone activity on Jan. 14, 2025, and described her as last seen in January 2025. Those details suggest investigators are still piecing together the final stretch of her movements. What is clearer is the length of the gap: Kloppenburg had been missing for more than 14 months by the time police excavated the garage. Authorities have not publicly explained why the alleged confession surfaced in March 2026 or how long investigators had considered Sullivan a possible focus in the case.
Neighbors watched as crews worked through the concrete and remained on scene for hours. Ella White, who lives nearby, told local reporters the digging extended into the evening, with investigators staying after dark. The house sits in a residential neighborhood, and the revelation that remains had been hidden under a garage floor left residents struggling to reconcile the allegations with the ordinary setting. Joseph McRell, another neighbor, said Sullivan had not struck him as dangerous. Those reactions underscored the way homicide cases often rupture community assumptions, especially when the alleged concealment is so close to everyday life. What had looked like a patched repair in a private garage became, according to prosecutors, one of the most important crime scenes in the region.
For Kloppenburg’s family, the discovery may bring the beginning of an answer, though not yet a final one. Her uncle, Steven Kloppenburg, said publicly that relatives believed the remains were hers even as they awaited DNA confirmation and autopsy results. Prosecutors said Sullivan is being held on a murder charge associated with a Jane Doe because the remains have not been conclusively identified in court records. He is expected to appear in Lowell District Court on Tuesday. Investigators have not announced a murder date, a motive, or whether they have found a firearm. Those unanswered questions are likely to shape the next phase of the case, along with forensic testing that could narrow the timeline and help define exactly what prosecutors say happened inside Sullivan’s orbit.
Authorities said Monday that the case now turns to the medical examiner, formal court proceedings and any additional evidence investigators may present after Sullivan’s arraignment. The next major public developments are expected to come from the courtroom and from forensic results confirming whose remains were found under the garage.
Author note: Last updated March 17, 2026.