Human remains found underneath the floor of a garage at a Massachusetts home during a homicide investigation are believed to be those of a woman who was last seen alive over a year ago, Middlesex District Attorney Marian Ryan said Monday.Ryan said the investigation that led to the discovery began on March 10, when Nashua, New Hampshire, police received a call from someone who said a friend told him he had killed a woman named “Jill.” The suspect was later identified as Shawn Sullivan, 40, of Tyngsborough. According to Ryan, the friend said that Sullivan “claimed that he had shot her and then buried her under the floor in a garage.” Ryan said detectives from the Tyngsborough Police Department, Tewksbury Police Department and Massachusetts State Police executed a search warrant at the home Sunday and discovered what appeared to be a large patched section of the garage floor measuring about 5 feet long and 3 feet wide.Investigators used ground-penetrating radar and confirmed something was located beneath the patched area before cutting through the concrete, Ryan said. They ultimately recovered a plastic bag containing human remains. Authorities believe the remains could be those of Jill Kloppenburg, a Lowell woman who was last seen in January 2025 and who was reported missing a month later, Ryan said. According to Ryan, investigators believe that Kloppenburg and Sullivan knew each other and that she had visited his home. Sullivan is currently being held on a murder charge connected to a “Jane Doe” because the remains are not yet positively identified. Ryan said that Sullivan is also expected to face other charges, including assault and battery with a dangerous weapon causing serious bodily injury and improper disposal of human remains.Sullivan’s arraignment is expected on Tuesday.

TYNGSBOROUGH, Mass. —

Human remains found underneath the floor of a garage at a Massachusetts home during a homicide investigation are believed to be those of a woman who was last seen alive over a year ago, Middlesex District Attorney Marian Ryan said Monday.

Ryan said the investigation that led to the discovery began on March 10, when Nashua, New Hampshire, police received a call from someone who said a friend told him he had killed a woman named “Jill.” The suspect was later identified as Shawn Sullivan, 40, of Tyngsborough.

According to Ryan, the friend said that Sullivan “claimed that he had shot her and then buried her under the floor in a garage.”

Ryan said detectives from the Tyngsborough Police Department, Tewksbury Police Department and Massachusetts State Police executed a search warrant at the home Sunday and discovered what appeared to be a large patched section of the garage floor measuring about 5 feet long and 3 feet wide.

Investigators used ground-penetrating radar and confirmed something was located beneath the patched area before cutting through the concrete, Ryan said. They ultimately recovered a plastic bag containing human remains.

Authorities believe the remains could be those of Jill Kloppenburg, a Lowell woman who was last seen in January 2025 and who was reported missing a month later, Ryan said.

According to Ryan, investigators believe that Kloppenburg and Sullivan knew each other and that she had visited his home.

Sullivan is currently being held on a murder charge connected to a “Jane Doe” because the remains are not yet positively identified. Ryan said that Sullivan is also expected to face other charges, including assault and battery with a dangerous weapon causing serious bodily injury and improper disposal of human remains.

Sullivan’s arraignment is expected on Tuesday.