Kid who pretends to be retarded to get off from a murder

The Good Son is a 2017 Philippine family drama television series starring Joshua Garcia, Jerome Ponce, McCoy de Leon, and Nash Aguas, with Eula Valdez, Mylene Dizon, John Estrada, Loisa Andalio, Elisse Joson, Alexa Ilacad and Albert Martinez.

A young boy stays with his aunt and uncle, and befriends his cousin who's the same age. But his cousin begins showing increasing signs of psychotic behavior.