A 56-year-old man was detained by police for four days after a nun’s life was threatened in a Brooklyn church.

Derrick Gadson of Brooklyn was arraigned and charged with aggravated assault in the second degree after he allegedly threatened to kill Mother Maria Amador as she was praying inside St. Joseph’s Co-Cathedral, Prospect Heights.

He was released and is due back in Kings County Supreme Court on Sept. 5.

The incident, which was caught on security camera, occurred July 5 at about 2:30 p.m. “I don’t believe in this because you don’t help poor people,” the shirtless man said to Mother Maria.

The 49-year-old nun, who is a native of Colombia, tried to ignore the man. When she tried to get the attention of another woman in the large church, the man said, “She can’t help you and I am going to kill you.”

When the man got closer to her, Mother Maria ran out of the pew and fled toward the front of the church.

“I thought, ‘This is my last day,’” she said. “Thank God I am safe. And I could run away.”

The man fled the scene, running out of the church and west on Pacific Street, according to construction workers on the block. Co-workers from the church tried to pursue the man but he had disappeared.

He was apprehended on a street not far from the co-cathedral the following morning at about 6:40 a.m. when he was recognized by a corrections officer from media reports.

He was taken to the 70th Precinct where it was determined that he had at least 40 prior arrests that included possession of drugs, burglary and felony assault.

Mother Maria was brought to the police station but could not identify the suspect.

“I forgive him,” said Mother Maria. “I think he needs help. He’s my brother.”

Mother Maria is a member of the Preachers of Christ and Mary, a Colombian-based group.