Two people were killed in a spate of stabbings Tuesday in Taunton, Massachusetts, authorities said.
Six people were stabbed in two separate locations, according to Bristol County District Attorney Thomas Quinn.
"Tragedy hit hard this evening," Taunton Mayor Tom Hoye said. "Hopefully we can make some sense of this."
Quinn said at a news conference that the series of stabbings began after a motor vehicle crash involving the assailant.
He then went inside a home, stabbing two women. One of them, an 80-year-old, was killed, and the other is being treated for "life-threatening injuries."
After the house incident, the assailant took a car and crashed it into the the front door of a Macy's department store at the nearby Silver City Galleria Mall.
He assaulted customers there and then made his way to Bertucci's restaurant in the mall, where he gained access to a knife and stabbed another four people, killing a 56-year-old man.
An off duty deputy sheriff happened to be on the scene and intervened, fatally shooting the assailant. The suspect was also killed.
"It appears but for the actions of the deputy sheriff, there may very well have been other victims," Quinn said.
The victims were taken to area hospitals for treatment.
A federal law enforcement source in Boston said the incident is being treated as a "criminal matter."
The FBI is aware of the situation and coordinating with state and local police, said Kristen Setera, spokeswoman for the Boston FBI field office.
CNN's Ralph Ellis, Deb Feyerick and John Newsome contributed to this report.
By Lawrence Crook and Joshua Berlinger