Police Commissioner Raymond Kelly told the AP that officers found 55-year-old Yannick Brea kneeling in the bathroom of her apartment. She had cuts to her head and was pronounced dead at the scene.
"In a bedroom was her son ... with a 3-foot sword," Kelly said.
Brea, 31, was arrested on charges of murder and criminal possession of a weapon. He was undergoing a psychiatric evaluation at a Brooklyn hospital, and police didn't know if he had a lawyer, the AP reported.
Neighbors said Brea was yelling biblical passages at his mother.
"I hear [Brea] chasing her through the house and he's just saying a bunch of [Bible] passages like, 'Repent, Repent, Repent,'" neighbor Gregory Clare told local television station WPIX 11 News. "I heard him chasing her through the house and I hear a loud scream and so I have my father call the cops, call 911."
Brea has no prior arrests, according to the AP. No previous domestic violence incidents had been reported at the home, police said.
Earlier, police spokesman Martin Speechley told TVGuide.com that Brea had to be subdued with a taser.