The Sept. 5 blast in Granville also injured three adults, including a 69-year-old woman who remained in critical condition.
GRANVILLE, Vt. — A propane leak caused an accidental house explosion that killed a mother and her 20-year-old son during a family birthday gathering in rural Vermont, state investigators said. Three other adults were injured in the Sept. 5 blast.
Vermont State Police identified those killed as Liam O’Sullivan, 20, and his mother, Sarah O’Sullivan, 46, both of Essex Junction. The explosion was reported at about 7:45 p.m. at a home on Connecticut Trail, off Post Office Hill Road in Granville, an Addison County community. Investigators with the Department of Public Safety Fire and Explosion Investigation Unit determined that propane leaking inside the home caused the explosion and classified the incident as accidental. Police said their investigation found no indication the blast was suspicious.
Liam O’Sullivan was pronounced dead at the scene, according to state police. First responders took Sarah O’Sullivan to Gifford Medical Center in Randolph, where she was pronounced dead. Autopsies were completed Sept. 6 at the Chief Medical Examiner’s Office in Burlington. Authorities said both died from injuries caused by the explosion.
Three other adults were taken to hospitals. Two suffered minor injuries, while Shiela Hammond, 69, of Granville, was critically injured. Vermont State Police said in its most recent public update that Hammond remained hospitalized in critical condition and was receiving treatment outside Vermont. Authorities did not publicly identify the two adults who suffered minor injuries.
Authorities have not released further details explaining how the propane escaped inside the house or what ignited it. The state police response included members of the Fire and Explosion Investigation Unit, Bureau of Criminal Investigations, Field Force Division and Victim Services Unit. The Vermont Division of Fire Safety and the Granville Volunteer Fire Department also responded.
The explosion happened while family members and others were gathered for a birthday celebration. WCAX reported that one of the two people who died was celebrating a birthday. Neighbor Brenda Buker told the station that she and her husband were having dinner with friends when they heard a loud boom and felt their home shake. She said items fell from the walls. Because fireworks had been heard earlier in the evening, those at her home initially did not realize a house had exploded.
Other nearby residents reported damage from the force of the blast, including a shattered window, according to WCAX. Buker said her property was not damaged. The explosion drew an extensive emergency response to the rural area, where investigators remained at the property as they worked to determine what caused the blast.
Sarah O’Sullivan had worked at the University of Vermont for 13 years, according to a remembrance published by the university’s Grossman School of Business. Her positions included work with Risk Management & Safety, the Rubenstein School of Environment and Natural Resources and the UVM Foundation. She spent much of her university career at the Grossman School and served as executive assistant to former Dean Sanjay Sharma. The school said she also pursued her own bachelor’s degree while working and raising her family.
The Grossman School said O’Sullivan’s death and the death of her son affected colleagues across the university. As of Sept. 12, Vermont State Police had not issued a later public update changing its finding that the explosion was accidental or providing a newer condition for Hammond. Investigators have said no further details about the cause were available.
Author note: Last updated September 12, 2026.