So, the end was like the end of the original Chucky story (SPOILER ALERT
In the original story of Child's Play by Dom Mancini, the kid was actually the killer. Considering that the kid was crazy about Chucky, they had the same clothes and almost the same size so when they show Chucky walking around or killing they never show the face, just the legs, or the back side.
Just at the end they revealed that the killer was the kid