Three people have been killed and four injured in attacks at a shopping mall and a home in Massachusetts, with the suspect among the dead.

Bristol County prosecutors said 28-year-old Arthur Darosa crashed a car outside a home in Taunton, south of Boston, walked inside and stabbed two women, one of them aged 80.

The 80-year-old was taken to hospital, where she later died. The other woman is being treated for life-threatening injuries.

Authorities say Darosa then drove to the Silver City Galleria shopping centre and crashed a car through the front of a Macy's store.

They say he assaulted multiple people inside the store before walking to a restaurant and stabbing four people, including a 56-year-old man who later died.

Investigators said an off-duty sheriff's deputy fatally shot Darosa.

A motive for the attacks remains under investigation, but state police said they have found no evidence of a connection to terrorism.

"There is no continuing threat to the public," said Dave Procopio, a state police spokesman.

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