A Good Samaritan is credited with saving three children from a convicted sex offender in Bay Ridge yesterday.

Just before 7 p.m., Steven McEvoy was walking down Fifth Avenue when he noticed three kids who appeared to be frightened. McEvoy says a man, who was later identified as Robert Collins, had his hand on one of the kids and was holding onto another.

McEvoy pulled one of the kids aside while Collins was distracted, and the child told him that Collins had been following them for hours, and that he claimed to be a police officer trying to arrest them and take them to Pennsylvania.

McEvoy says he shouted at Collins and chased him around bus depots on the corner of Bay Ridge Parkway and Fifth Avenue. The Good Samaritan then told the kids to run and get help.

Collins was later arrested and charged with criminal impersonation of a police officer, luring a child to commit a crime and acting in a manner injurious to a child younger than 17 years.

Collins' stepdaughter said in a statement that he's a decorated retired NYPD officer who had spent over 35 years on the force and that he would never harm a child.

However, the NYPD says Collins worked with the department for only two years in the 1970s.