Tyngsborough Man Charged After Human Remains Found Buried Under Garage Floor

Shawn Sullivan, 40, of Tyngsborough, Massachusetts, was ordered held without bail Tuesday after human remains believed to be those of Jill Kloppenburg, a 47-year-old Lowell woman missing since January 2025, were recovered from beneath the concrete floor of his garage on Audrey Avenue.

The case broke open not through forensic surveillance or a routine welfare check, but through a confession Sullivan allegedly made to a friend. That friend contacted Nashua, New Hampshire police and reported that Sullivan said he had shot and killed a woman named Jill at his home around January of last year and buried her under the garage floor. Nashua police connected the account to Kloppenburg, who had been reported missing to Tewksbury police in February 2025 and entered into a missing-persons database. The FBI had separately logged her last seen leaving her Lowell home on January 2, 2025; the last communication through her cell phone, according to the Middlesex District Attorney's Office, was January 14, 2025.

Detectives from the Tyngsborough Police Department, Tewksbury Police Department, and Massachusetts State Police executed a search warrant at the Audrey Avenue home on March 15. Inside the garage, investigators noticed a large patched section of the concrete floor measuring approximately 5 feet long by 3 feet wide. They used ground-penetrating radar to scan the full garage floor and confirmed that something was located beneath that patched area before cutting through the concrete. What they recovered was a plastic bag containing human remains.

Prosecutor Ceara Mahoney laid out Sullivan's alleged account at his court appearance. "The defendant said he was with Jill and holding a firearm while falling asleep. At some point, he made a jerking motion, which caused him to pull the trigger, discharging a firearm and shooting Jill in the chest. He stated that Jill soon died and if there was a chance for her survival, he would have called for help. Instead, the defendant kept Jill's body in his room for a couple of days. He then brought Jill's body to the garage where he dug a hole in the concrete, placed her body in the hole and then filled the hole," Mahoney said.

Sullivan and Kloppenburg were friends, Middlesex County District Attorney Marian Ryan said, and investigators confirmed that Kloppenburg had been inside the Audrey Avenue home and was with Sullivan around the time she disappeared. Sullivan faces charges of murder, assault and battery with a dangerous weapon causing serious bodily injury, and improper disposal of human remains. A lawyer representing Sullivan declined to comment.

While some outlets reported the remains were formally identified as Kloppenburg's, the DA's office stated that formal DNA identification was still pending as of the charges announcement, with the medical examiner working to determine the official cause and manner of death.

Tyngsborough Police Chief Shaun Woods addressed the outcome at a press conference. "This is a person, a loved one, who was reported missing, whose disappearance remained under active investigation for over a year," he said. "This is never the outcome we want in public safety, but we take solace in the fact that through the hard work of investigators, a suspect is now in custody."

Sullivan was arraigned in Lowell District Court. The medical examiner's findings and formal identification results have not yet been publicly released.