The Middlesex County says a 911 call was placed around 1 p.m. for an emotionally disturbed person who was on Hall Avenue.
The acting prosecutor in Middlesex County says that the man, Dixon Rodriguez, came after a police officer.
The officer fired his weapon and afterwards, police found a knife on Rodriguez.
The prosecutor says that they saw the incident unfold, including seeing the knife, on surveillance video.
The surveillance video has been taken into evidence.
Because of the shooting, schools in the surrounding area were put on lockdown.
People who know Rodriguez described him as learning disabled, kind, trusting, innocent, and a beloved fixture on that street, Hall Avenue.
Rodriguez had a mild case of schizophrenia, according to relatives. He couldn't work, but was not violent, they say.
"He didn't bother nobody. He didn't have any weapon, that's a big lie. I think the police officer overreacted," a neighbor said.
"He had his hands in his pockets, all the time, he had his hands in his pockets," Rodriguez's aunt said.
The prosecutor said that is not the description of the man that police encountered.
"There were two officers who responded, they attempted to engage the subject. You could see that there was a conversation. The subject at one point attacked one of the officers, at which time shots were fired and the person died subsequently. We have recovered a weapon from the decedent's hand," said Andrew C. Carey, acting Middlesex Prosecutor.
"I was talking to the crossing guard what was happening and what was going on before they shot him. And before the crossing guard got to answer me, the police officer, the girl one, shot him, let go of her firearm right away and put her hands and said, 'I thought, I thought he had something,'" said Brenda Munoz, an eyewitness.
The investigation continues.