Officials reveal cause of fire that led to beloved Boston firefighter’s line-of-duty death

BOSTON — The cause and origin of the fire linked to the line-of-duty death of a beloved Boston firefighter have been revealed.

Robert Kilduff Jr., a third-generation firefighter and U.S. Marine veteran, died while responding to a fire on Treadway Road in Dorchester in May after falling from a third-floor porch. He was rushed to the hospital, where he later died from injuries sustained in the fall.

“We recognize this incident has had a profound impact on this department, the Kilduff family, and the entire Boston community,” said Boston Fire Commissioner Rodney Marshall.

“We thank the family and the community for their patience as our investigators worked diligently to establish the origin and cause of this fire.”

Investigators determined the fire was caused by thermal runaway involving multiple lithium-ion batteries stored in plastic toolboxes.

“These batteries much be charged, handled and stored in accordance with the manufacturer’s recommendations and established safety guidelines,” said Marshall.

“Improper charging or storage can create serious fire hazards.”

Lithium-ion batteries are commonly used in phones, computers, power tools and electric vehicles.

“I don’t want to scare people away from them, but they do pack a lot of energy,” said District Fire Chief Keith Kelly of the Boston Fire Department’s Special Operations Command.

“As long as you’re using them properly with the recommended packages’ guidelines, they’re safe.”

Kelly offered several steps people can take to reduce the risk of fires:

• Use the charger the battery came with and charge it on a stable surface.
• Use the battery for what it’s meant for.
• Make sure batteries are certified by a nationally recognized testing company.
• Look for leaks and corrosion, and do not charge a battery if it appears compromised.
• Do not throw batteries in plastic trash bins.
• Avoid exposing batteries to the elements.
• Never charge e-bikes, hoverboards or other electrical equipment inside a front door.

Although the investigation into the cause and origin of the fire is complete, investigations into Kilduff’s line-of-duty death remain ongoing.

The National Institute for Occupational Safety and Health is conducting one investigation, while the Boston Fire Department Board of Inquiry is conducting another into the circumstances surrounding Kilduff’s death.

“Bobby Kilduff gave his life in the line of duty doing what our firefighters do every day, putting themselves in harm’s way to protect their neighbors in our community,” said Mayor Michelle Wu on Wednesday.

“He made the ultimate sacrifice in service to our city and were continuing to work on several efforts to honor his legacy and support his family.

Facts and findings from the investigations into Kilduff’s death will be released once they are complete, according to the fire marshal.

This is a developing story. Check back for updates as more information becomes available.

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