TYNGSBOROUGH — A Tyngsborough man has been charged with murder after investigators discovered human remains believed to be those of a Tewksbury woman who had been missing for more than a year buried beneath the floor of a garage.
Middlesex District Attorney Marian Ryan and Tewksbury Police Chief Ryan Colunbus announced today that Shawn Sullivan, 40, of Tyngsborough, was charged with murder, assault and battery with a dangerous weapon causing serious bodily injury, and improper disposal of human remains.
Sullivan was arrested by Tyngsborough police on March 15, 2026, and is expected to be arraigned in Lowell District Court on March 17, 2026.
According to the Middlesex District Attorney’s Office, on March 10, 2026, Nashua, New Hampshire police received a call from a man who said his friend, Shawn Sullivan, told him that, in or around January 2025, he shot and killed a woman named “Jill” at his home on Aubrey Avenue in Tyngsborough, and buried her beneath the floor in the garage.
Through a missing persons database, Nashua police identified a missing woman named Jill Kloppenburg, who had been reported missing to the Tewksbury Police Department in February 2025. Investigators later determined that Sullivan allegedly knew Kloppenburg, that she had been in his residence, and Sullivan had been with her around the time of her disappearance.
On March 15, 2026, detectives from the Tyngsborough Police Department, Tewksbury Police Department and Massachusetts State Police executed a search warrant at Sullivan’s home on Audrey Avenue in Tyngsborough. Inside the garage, investigators observed what appeared to be a large patched section of the floor.
Using ground-penetrating radar technology, investigators scanned the garage floor and identified an area that appeared to have been cut and patched. Investigators then cut through the floor of the garage and recovered a bag of human remains.
The remains have not yet been formally identified, and the Office of the Chief Medical Examiner will attempt to determine the cause and manner of death as well as confirm the victim’s identity, the Middlesex District Attorney’s Office said in a statement.
In a statement issued on March 16, 2026, Tewksbury Police Chief Ryan Columbus said investigators believe the remains are those of Kloppenburg.
“Yesterday, the Tewksbury Police Department assisted in locating remains believed to be those of Jill Kloppenburg, a Tewksbury resident who has been missing for more than a year, in Tyngsborough,” Columbus said in the statement. “This is not the outcome anyone hoped for, but we are grateful Jill’s family and friends can finally have answers and some measure of peace and closure.”
Chief Columbus offered condolences to Kloppenburg’s family and said members of the department’s Criminal Investigation Division had continued working the case and following leads for more than a year.
“On behalf of the entire Tewksbury Police Department, we offer our sincere condolences to Jill’s loved ones,” Columbus said. “Our thoughts are with her family and friends during this incredibly difficult time.”
The Middlesex District Attorney’s Office said in a statement released on March 16, 2026, that “this is a very active investigation” and encouraged anyone with information about Kloppenburg to “immediately contact” Massachusetts State Police at (781) 897-8300.
