Police said the 31-year-old actor apparently had an argument with his mother and began stabbing her. Neighbors reported hearing a man yelling Bible passages during the attack.
"I heard this wild screaming," Gregory Clare, who lived in the building, told the Daily News of New York. He said he heard screams of "'Repent, repent, sinner, sinner,' over and over again," and "'You never accepted Jesus."'
Michael Brea was taken to Kings County Hospital for psychiatric evaluation.
He has no prior arrests, and Kelly was not sure if he had a psychiatric history. No previous domestic violence incidents had been reported at the home, police said.
The Associated Press contributed to this report.