Each event is set at different times through the night, with nights 1, 2, 3 and 4 occurring in 1987, while nights 5 and 6 occurring during 1964. From the events that occur when the Player finishes a night, each time an event happens which takes place in a "Robot Factory" which first starts off with nothing in the room, until after the 2nd night, starting off with audio, until a giggling sound of a child, followed by screaming and the sound of flesh being ripped apart which happens in the background, until a few seconds later, the footage appears, and what is visible are pieces of Endos covered in blood.
After the third night, it shows the event which happened but has police tape around it, and numbered Endo parts on the track, however, after the fourth night's event, the room shows Cindy and Candy sitting on the track, indicating that two children may have been murdered, and were made into the two animatronics.
After the 5th Night, the room is shown again, but the room is set years before the other cutscenes, as can be known because the camera is old fashioned. The room has Old Candy and Blank sitting on the track, they are both in mint condition.
After the 6th Night, the room with the same animatronics or maybe three animatronics, shows Old Candy, Blank and Rat. The date is different as it is set in the 1964's. Rat then stands up, and walks out, leaving Blank and Old Candy there until 1987. It is revealed by the Secret Minigame, Cindy's Whack-A-Mole, that RAT actually killed the two children with some help from the CAT.
The Previous Guard which was known as "Crazy" may have killed the two children, as he was known to be crazy, and would slaughter people, especially children. It is also possible the two kids may have been someone close to the Guard.
Rat also may have killed the kids because he was decommissioned. Therefore, possibly hiding the truth, many people think this. The Third game reveals that it was CAT who killed them and turned them into Candy and Cindy while Shadow Rat which is RAt in his noncorporal / out of animatronic form just watches him.